DEAR BOB: We recently applied for a mortgage loan. It was worse than getting a job. The loan officer treated us as if we were crooks. After stalling on our application for three weeks, he had his secretary phone us to say our application was "declined" because the property didn't "appraise out." I know that the house is worth what we offered because the agent showed us several similar houses that cost more. Is this typical or did we just get a bad loan officer? Todd Y., Washington.

DEAR TODD: Don't feel bad. The same thing happened to me several years ago at the world's largest bank. Yet I got exactly the same loan, requested from another lender just a few days later. Some lenders are just downright unpleasant and intimidating, as you found out.

There is a big difference among mortgage lenders. Apply for mortgage loans at more than one place at the same time. Lenders dislike your doing this, but it's the only way for the borrower to protect against lenders such as you encountered.

Don't become discouraged unless every lender in town turns down your application. If that happens, and you included a financing contingency clause in your purchase offer, then your earnest money deposit will be refunded.

DEAR BOB: To qualify for that installment sale tax deferral, does the 30 percent maximum down payment apply to the net or gross sales price? Max G., Springfield.

DEAR MAX: The gross sales price, not the net, is used to determine installment sale qualification. If you qualify, your profit tax will be spread out over the years you receive your buyer's payments, rather than having to pay it all in the year of the sale, thus boosting you into a high tax bracket.

Installment sale rules require the property seller to receive not more than 30 percent of the gross sales price in the year of sale. Major sources of these "payments received" include the buyer's cash down payment, principal payments on the installment sale mortgage and any "excess mortgage" (old mortgage exceeding seller's adjusted cost basis) taken over by the buyer. Ask your tax adviser to explain further.

DEAR BOB: I like to speculate in land investments. Are there any good books in this field that give details on investing techniques? Mr. a. k., Reston.

DEAR MR. A. K.: Yes. Land speculation is one of the riskiest ways to make real estate profits. You'll need all the help you can get.

Four good books on land investing are: "How to Build a Fortune Investing in Land," by John E. Kirk (Prentice-Hall); "How to Reap Riches from Raw Land," by Glen Nicely (Prentice-Hall; "All About Land Investment," by William Benke (McGraw-Hill) and "Finding and Buying Your Place in the Country," by Les Scher (Collier-Macmillan Books). All four are available at larger libraries and bookstores.

DEAR BOB: I read in the newspaper that average home sale prices dropped slightly. Does this mean we're due for a crash in home prices? Should I sell mine now? Ela M., Fairfax.

DEAR ELA: No. Don't be fooled by the cycles of real estate prices that are dependent on the availability of mortgage money at affordable interest rates.

Home sale prices should continue their gradual upward trend. However, there will be more plateaus along the way, as there have been in the past. Local economic conditions, such as factory layoffs due to the government's monetary policy, may cause temporary slight price drops where more people want to sell than buy.

Fortunately, most home sellers don't have to sell, so they can comfortably ride out any local temporary home sale oversupply. Unless your home is in a declining slum area, it will probably continue to appreciate in value, but not as rapidly as during the last few years. Don't sell unless you must.

DEAR BOB: For several months we've been looking for a home to buy. A realty broker phoned us about a "distress property." The tenants aren't paying the rent and the landlord got behind in his mortgage payments. The house is pretty dirty, but we can buy it for just a $7,000 down payment, plus taking over the old mortgage. Do you think this is a bad deal? Jose R., Washington.

DEAR JOSE: No. If you don't want that house, thousands of other home buyers do, if it's well-located and in reasonably sound structural condition. When you see a good buy, buy it fast before someone else does.

DEAR BOB: At today's high mortgage interest rates, we can barely qualify for a home loan. One realty agent said that if we take a home loan at 12 percent interest and if we are in a 30 percent income tax bracket, our after-tax cost is only about 8 percent. If this is true, how did she figure? Sue M., Rockville.

DEAR SUE: The realty agent is almost correct. To estimate your after-tax mortgage interest cost, multiply the mortgage interest rate by your income tax bracket and subtract this figure from the loan's interest rate.

For example, 12 percent multiplied by your 30 percent income tax bracket is 3.6 percent. That represents your income tax saving for the itemized income tax deduction for the mortgage interest. Subtracting 3.6 percent from 12 percent yields 8.4 percent, your after-tax cost of that 12 percent loan. Your tax adviser can give you further details.

DEAR BOB: Last year we bought a house in California where we plan to move after retirement next year. I am 63 and have lived in our present home more than 20 years, so we can qualify for that $100,000 home sale tax exemption. Without losing the tax break, can we rent out our present house for a year or two so we can move to California to see if we like it there before we sell the old house? Lou V., McLean.

DEAR LOU: Yes. Your situation is a perfect example of why the "over 55 rule" $100,000 home sale tax exemption has a minimum ownership-occupancy requirement.

To qualify for this tax break, the seller must have owned and lived in his principal residence any three of the five years before sale. In addition, of course, the seller must be 55 or older on the title transfer date.

The three-out-of-five years requirement will allow you to move to California and rent out your old home for up to two years before selling, without losing the $100,000 tax exemption. Your tax adviser has further details.

DEAR BOB: We bought a two-bedroom condo for $26,500 and it is now worth at least $48,000. Since our family has grown, we moved to a rented house and have rented our old condo to tenants. Should we refinance the condo mortgage or take out a second mortgage to get cash to buy a house to live in? Barbara E., Silver Spring.

DEAR BARBARA: It is difficult to refinance nonowner-occupied houses and condos now. The reason is most banks and savings associations are selling their new mortgage loans in the secondary mortgage market and that market is limited to loans on owner-occupied residences. However, second mortgages are readily available on income property, so that is probably your best bet today.