If you're one of the estimated several thousand home sellers around the country who got caught in the mortgage-market "point squeeze" of the past three weeks, you now know the sobering cardinal rules of dealing with FHA/VA-backed loans:

First, make sure your sales contract doesn't lock you into paying a potentially big chunk of your purchaser's financing charges without your knowledge or control.

Second, be certain that you, your realty broker or attorney have taken a hard look at where FHA/VA rates are pegged, relative to the rest of the market. Your would-be buyers may be signing up eagerly for bargain-rate government-insured loans for 30 years. On closer inspection, however, you'll find the bargain may be completely at your expense.

Officials at the federal Department of Housing and Urban Development here concede in private discussions that the agency misread the market during the latter half of May and the first week of June.

FHA's and VA's maximum allowable rate on home loans--set by HUD--was dropped to 11 1/2 percent and kept there until June 8. Meanwhile, rates in the conventional, non-government-insured market headed in the opposite direction. They hit 13 percent in the national secondary market by late May.

HUD didn't raise its statutory loan-rate ceiling for nearly two weeks after that, and then pushed it to 12 percent, where it sits at present.

The federal agency's slow reaction time wouldn't have cost consumers, lenders or real-estate brokers a cent if it weren't for one problem: Home buyers who use FHA/VA financing aren't allowed to pay more than one "point" of the extra financing fees tacked on by lenders to bring government-insured loan rates up to going market levels.

Home sellers, on the other hand, get no such regulatory protection. They can be stuck with all the fees above that limit--sums that can run into the thousands of dollars and get sliced from the seller's sales proceeds. (A "point" is equal to 1 percent of the principal loan amount, and is normally paid in cash at closing. A one-point fee on a $75,000 mortgage is $750. Six points on the same loan costs $4,500.)

Just before HUD hiked its rate to 12 percent, some lenders were demanding eight points or more on FHA/VA loan commitments at 11 1/2 percent. "You can imagine what that did to sellers," says Thomas Shealy, president of Trust Company Mortgage Corp., a major Atlanta lender on FHA/VA loans. "They either hit the ceiling or stampeded like antelopes."

If their sales contracts didn't contain protective language limiting the points they'd pay to three or four, they gritted their teeth and got less for their home than they'd planned, said Shealy, simply because of the slow decision-making of a government agency in Washington.

If their sales contracts did contain seller point limits, on the other hand, HUD's 11 1/2 percent rate "blew an awful lot of scheduled closings out of the water." Trust Company Mortgage Corp.'s volume of FHA/VA loan closings, for example, dropped by 50 percent during the period when points hit the five and six range.

And properly so. If you were the seller of a house carrying a contract price tag that included compensation for two or three points, and suddenly were faced with the prospect of getting $4,000 to $5,000 less for your house, what would you do?

Shealy puts the answer bluntly: "I'd get the hell out of that deal fast--if I could." A friend of Shealy, a business executive based in Seattle, did precisely that two weeks ago, even though it meant delaying the long-planned move of his family to the East Coast.

The chief economist of the National Association of Home Builders, Michael Sumichrast, also caught the wrong end of the FHA/VA rate cycle. Sumichrast and his wife, Marika, long have invested in single-family rental homes in the suburbs of the nation's capital. They had planned to refinance a portfolio of 14 homes at FHA's attractive 11 1/2 percent rate in May--but canceled the whole transaction when financing charges began to skyrocket.

Ironically, many consumers attracted by FHA/VA financing--particularly its fixed-rate, low-down-payment features--aren't aware of an experimental negotiated-rate plan offered by the agency as an alternative to the rate roulette of the past month.

HUD can insure 50,000 negotiated-rate loans this fiscal year, permitting sellers to lock in rates and points in advance. Local realty brokers or lenders should be able to tell you whether the negotiated-rate option is available in your area.