Real estate agent Jennifer Hernandez knows about the squeeze that military families, faced with a transfer to a new place of duty, are feeling these days because the homes they bought during the housing boom are “upside-down” — worth less than the balance owed on their mortgages.

These families don’t have the option of just staying put — a service member can’t just say “no thanks” to a change of station, as it’s known in the military — so they face the prospect of a short sale or foreclosure because a normal sale probably wouldn’t yield enough to pay off their loans.

Hernandez hears their stories. She advises them of their options. But she’s more than just a sympathetic professional: She’s in the same boat.

And she’d like to get the word out that this is a widespread problem for military families today.

“People who serve this country can’t have the same American Dream as the ‘normal’ American family,” said Hernandez. “They’re reasoning, why in the world did I ever buy a home? Why didn’t I rent?”

Hernandez, an agent with Liz Moore & Associates in Williamsburg, Va., specializes in working with military clients stationed at the numerous military installations in the Hampton Roads area.

Her husband, Tony, is an Air Force officer, and the couple have moved 16 times in the past 20 years. In a few months, he’ll transfer to a base in Alabama, but this time she’ll stay behind at least for a while, she said — not only do they want to keep the kids in the same school, but they’re significantly upside-down on their own home. They’ve elected to wait it out.

“I know at least 20 people who are in this position, just in the Hampton Roads area,” she said.

And she’s heard from many, many more from around the country and around the world since she was quoted about this particular financial bind in a local newspaper article — that report was picked up by numerous other news outlets.

Hernandez is gathering their stories, to be passed on to Holly Petraeus (wife of U.S. Army Gen. David Petraeus), who recently was appointed to head an effort to start an Office of Servicemember Affairs, which will focus on the financial aspects of military life as a part of the new Consumer Financial Protection Bureau.

“I’m involved with the National Military Family Association (a private, advocacy organization), and she and I got into a conversation in a meeting in February,” she said of Petraeus. “I told her about my own situation, and I told her about how many active-duty families were in the same situation.

“She said she wanted to hear any kind of stories that I could forward her to bring to the Office of Servicemember Affairs,” Hernandez said. “I’m trying to bring to light how many people this is happening to.

“There’s no viable solution for this problem right now, but I’d like to get people realizing that it’s a national problem, not a local problem.”

Some transferring military personnel in upside-down real estate situations do have access to aid from the federal government, she said.

The Department of Defense’s Homeowners Assistance Program, or HAP, has funding to reimburse qualifying service members for part of their losses from their home sales, if they don’t have funds from a sale to pay off their mortgages, or assist in the event of a default, she said.

And though that program has helped thousands of homeowners, she said, it has a catch: It’s available only to military personnel who bought their homes before July 1, 2006, and were reassigned between Feb. 1, 2006, and Sept. 30, 2010.

“Most everybody here that I know bought their homes in 2007 and 2008, when the local market was at its height,” she said. “There’s a bill in the House of Representatives to extend the dates of the program, but it doesn’t have a lot of support right now.”

Hernandez said she’s not looking for a large-scale bailout to aid military families, but to expand the current law’s scope to help those who are obligated to move.

“Most of these families would have to come to the closing table with $30,000 or $40,000 if they were to sell,” she said.

The real estate needs of military personnel are much different from those of average consumers, Hernandez said.

“A service member moves every two to four years,” she said. “They don’t have a choice on the time or the location.”

And the whole process can happen very quickly and with its own set of tensions, said Hernandez, who said she became a real estate agent two years ago, as she often found herself offering practical advice to other military families because of her extensive experience with the process.

“A lot of times, the military families find out they’re moving and have only days to fly out somewhere and rent or buy a home,” she said. “You’ll usually just get one of the two spouses (looking for a residence), because the other one has to stay home and get ready to move.”

Plus, most military families can’t afford to have both spouses go on the hunt: Though the military grants the transferring service member time off to go house hunting, it doesn’t cover what might be a pricey airline ticket for the search.

Hernandez said that real estate agents who are knowledgable about military life could find themselves in demand.

“When I came to Virginia, I couldn’t find an agent who had an understanding of military members,” she said. “You want somebody who understands your needs. They’re going to start talking in acronyms, and if you don’t have a clue, it’s not going to help them.”

“The military is my niche — it’s my passion, and I understand it,” she said.

She blogs about the real estate concerns of local military families at WilliamsburgMilitaryInsider.com and she is on a “military team” at her brokerage, which is also developing a rental program targeted toward service members.

“I’ve had military members come into the area who told me they were going to buy, but as soon as they decided to go into a rental instead, their agents dropped them,” she said.

With the economic downturn and with the hard lesson of upside-down mortgages, “rentals are becoming a hot item these days in this area,” she said.

She’s advised almost all of the transferring military families who have sought her counsel that they should consider whether to rent out their homes and hire a property manager. Short sales, apart from being very time-consuming, can hurt a homeowner’s credit score — which can be additionally damaging to military personnel who have to maintain security clearances, Hernandez said.

How the military is going to regard those particular credit dings from this recent real estate phenomenon isn’t entirely clear at this point, she said.

“It’s a new issue — nobody knows the effects,” she said. “I tell people, ‘Are you going to take that risk?’ ”

Hernandez’s husband has high security clearances, which affected their whole approach to homebuying; he needed to avoid significant debt, she said.

“We did a (Department of Veterans Affairs) loan, we don’t have a second mortgage, we bought down our interest rate,” she said. “We did the research and we did it conservatively, but we’re still upside-down.”

So, he’s off to Alabama while she stays behind with the kids and the house, she said. If they don’t sell it in a year or so, they’ll probably rent it out.

“We could get a loan (to make up the difference to sell our home), but we’re not going to incur the debt, and we’re definitely not going to do the short sale because it would affect our credit,” she said.

Mary Umberger is a freelance writer in Chicago.

 A frequently asked question is whether a mortgage borrower receives any benefit from paying before the due date. In most cases, the answer is “no,” but there are a few exceptions. With simple-interest mortgages, including HELOCs (home equity lines of credit), it does pay to pay early and, under some circumstances, paying early in order to shift next year’s interest into this year could reduce taxes.

The rules when payments are late: On a standard monthly payment mortgage, the payment is due on the first day of the month, and will be credited to the borrower on that day, regardless of when it is received. If the payment is received within the grace period, customarily the first 10 or 15 days, the borrower receives a free ride — no interest accrual — for those days.

If the payment is received after the grace period but within the month, the borrower is subject to a late charge. If the payment is not received until the following month, the borrower incurs a late charge and is reported to the credit bureaus as a 30-day delinquency, but the payment is credited as of the first day of the previous month.

When payments are early: Payments made before the due date are also credited as of that date. This gives the lender free use of the borrower’s money for that period. The borrower who consistently pays two weeks early, for example, is in effect providing the lender with a two-week grace period comparable to that provided by the lender to borrowers who pay late. There is no benefit to the borrower.

Simple-interest mortgages are different: On simple-interest mortgages, interest accrues daily rather than monthly, which changes the rules significantly. As with standard mortgages, payments are due on the first day of the month and late fees are charged on payments received after the grace period.

On simple-interest mortgages, however, interest is due every day. This means that a borrower who pays one day late pays additional interest for that day, and the borrower who pays one day early saves a day’s interest.

The bottom line is that a borrower who consistently pays two weeks early will save money on a simple-interest mortgage. That doesn’t bother the lenders because they know that those are rare birds. Most borrowers pay late.

Borrowers don’t get to choose between standard and simple-interest mortgages; I have never heard of it being offered as an option. Most have standard mortgages, and those with simple-interest mortgages typically didn’t know what they were getting. Borrowers need to adapt their payment habits to the kind of mortgage that they have.

I should note that HELOCs are simple-interest, and most HELOC borrowers do understand that they accrue interest daily. It pays to pay early on a HELOC.

Making advance provision for future payment: Early payment should not be confused with making advance provision for future payments. When I took my family on an around-the-world tour some time ago, I left a set of checks with the loan servicer dated at monthly intervals. This assured that each payment would be made on time, but I was not giving the servicer the use of my money because only one check at a time became negotiable.

A potential tax benefit in paying early: In December, some borrowers who itemize their deductions make their payments for the early months of the following year. This shifts the interest deduction in those months from next year to this year. This can be especially advantageous if the borrower expects to be in a lower tax bracket, or expects the tax rate to be lower next year.

For this to work, however, you need the servicer to agree in advance to credit your account this year for the payments due next year. The end-of-year statement will then show the interest as having been paid this year.

The writer is professor of finance emeritus at the Wharton School of the University of Pennsylvania. Comments and questions can be left at www.mtgprofessor.com.

 Home-sale problems usually derive from three sources: property inspections, the buyer’s financing, or the appraisal of the property. Any one of these can crater a deal. Being proactive is the secret to avoiding problems, if possible.

It can’t be emphasized too much how important it is to have the property fully inspected by qualified local inspectors. Check the permit history and ask the sellers for answers to any questions you have.

Along with this, sellers should disclose what they know about the property that might impact a buyer’s decision to buy or the price she’d pay, even if not required to do so by law. State disclosure laws vary from one state to the next.

Sellers who fear that telling all will keep their home from selling should consider the consequences of concealing something negative, like a leaky roof or a basement that floods when it rains. Withholding information and getting sued later is likely to be far more costly and time consuming than coming clean even if you have to make a price concession to compensate the buyer for defects she’ll need to repair.

Low appraisals have been plaguing the home-sale industry for a few years. One issue is the lack of comparable sales. Another is that prices have declined in most areas since 2007. As a result, many homes appraise for a price that’s lower than the amount of the loans secured against the property. This can turn a conventional sale into a short sale that takes time and can be difficult because the sale requires lender approval.

HOUSE HUNTING TIP: It’s a good idea for both buyers and sellers to study the recent comparable sales for the home in question. Discuss the comparables with your agent and make sure you have comparables ready for the appraiser or buyer’s agent before the appraiser inspects the property. Some appraisers are from out of area and don’t know the local market.

Sellers should consider not selling if there aren’t comparable sales to support the price they want. A seller can hope for an all-cash buyer, but even all-cash buyers often want the home to appraise for the contract price.

If the contract includes an appraisal contingency, the buyer can withdraw from the contract without penalty if the appraisal comes in low. Sellers who choose to go ahead and market their home at a high price should be prepared to negotiate the price with the buyer if the appraisal is low.

Before making an offer to buy a home, talk to your mortgage broker or loan agent and find out what you can afford. Lenders’ qualifying guidelines have become more rigorous in recent years, and they are about to tighten further. Be candid with your mortgage originator so that there are no last-minute surprises.

It’s best to get preapproved for the mortgage you’ll need before you make an offer. This will help in your negotiations with the sellers. It will increase their comfort level about your ability to actually close the transaction.

Preapproval involves having your loan package reviewed by a lender’s underwriter. This means that you’ll have to assemble all the paperwork the lender requires. Be prepared to provide even more than you could possibly have imagined would be necessary.

You can avoid problems by using an experienced local agent who comes highly recommended. Local agents are aware of local problems, such as slide areas, that might not be known to an out-of-area agent. Set your standards high and expect the best.

THE CLOSING: Residential purchase contracts need to be in writing to be binding. If any changes are made during the transaction, they should be in the form of a written addendum to the contract signed by both buyer and seller.

Dian Hymer, a real estate broker with more than 30 years’ experience, is a nationally syndicated real estate columnist and author of “House Hunting: The Take-Along Workbook for Home Buyers” and “Starting Out, The Complete Home Buyer’s Guide.”