DEAR BOB: Do you think home prices will crash? I read in the newspaper something about price decreases. But i talked to a realty agent who said she hadn't heard of any sellers taking any losses. But she did say sales are slow now. What do you think? Sally W., Washington

DEAR SALLY: Don't be misled. It's true the median and average home sale prices in many towns are dropping. Sales volume is down too. It's still a buyer's market and a great time to buy, often with excellent seller financing terms.

The problem is the difficulty of obtaining large mortgages on the more expensive homes. Homes are selling but take longer to sell than in the past.

Fortunately, home values are not like the stock market where fortunes can be lost quickly. Real estate prices are not subject to panics, or advice of a newsletter writer, as can happen in the stock market.

DEAR BOB: Years ago my wife (now age 77) and I (now age 82) used a tax rule which gave us a $20,000 tax exemption when we sold our house. Now we have sold our condominium and will move to a retirement community where we won't own our home. Our sale profit will be about $26,000. Can we use that $100,000 "over 55 rule" tax exemption you often mention, even though we previously took a $20,000 exemption? Mac C., Alexandria

DEAR MAC: Yes. If you used the old, now repealed "over 55 rule" tax exemption before July 26, 1978, you can still use the current over 55 rule" $100,000 home sale tax exemption. But you must have owned and occupied your principal residence at least three of the five years before its sale to qualify.

Further details are in my special report "Everything You Want and Need to Know About the $100,000 Home Sale Tax Exemption." To obtain a copy send a $2 check payable to "Newspaperbooks" for Report 80107 to The Washington Post, P.O. Box 259, Norwood, N.J. 07648.

DEAR BOB: Some time ago you gave the amount of the net estate a person can leave without owing any estate tax. What is that amount? Mrs. D.A., Fairfax

DEAR MRS. D.A.: Persons dying in 1980 could leave net estates up to $161,563 free of federal estate tax. This exemption increased to $175,625 for persons dying in 1981 and thereafter.In addition, assets left to a surviving spouse are exempt up to the greater of $250,000 or one-half the value of such assets.

To illustrate, a decedent in 1981 can leave at least $425,625 in assets ($175,625 plus $250,000) to a surviving spouse without any federal estate tax. Ask your tax adviser for further details.

DEAR BOB: Two years ago when we bought our home, we got a new S&L mortgage for 90 percent of the purchase price. I recall that the lender said our loan would be insured. Two months ago my husband died, at age 43, of a heart attack. I notified the lender, expecting the insurance to pay off our mortgage. But the lender says our insurance only pays the lender for loss suffered upon foreclosure. Is the insurance company trying to get out of paying off the mortgage? Anne Marie A., Springfield

DEAR ANNE MARIE: No. You've got two different kinds of insurance mixed up. When you obtained your mortgage, you were required to buy private mortgage insurance (PMI). Your policy insured the lender against mortgage foreclosure loss.

If you wanted insurance to pay off your mortgage in the even of your husband's death, you should have purchased life insurance on him. Such insurance policies, often called mortgage insurance, are frequently offered to buyers at the time of home purchase by insurance agents.