DEAR BOB: I am over 65. How much tax deduction will I get on the sale of my rental property? Charles H., Chevy Chase.

DEAR CHARLES: None. The "over 65 rule" applies only to the sale of your principal residence. It makes the profit on the first $35,000 of the sale price tax-free. To qualify, you must own and live in the residence at least five of the eight years before sale, be 65 or older on the transfer day and never have used this tax break before. Ask your tax adviser for details.

DEAR BOB: How do you explain borrowing money to people who feel they must have all their money in the bank? Ted H., Washington.

DEAR TED: I'm thankful for people who foolishly leave their idle money in banks. They make it possible for the rest of us to borrow mortgage money to make real estate profits.

Suppose a saver earns 8 percent interest on his savings certificate. Inflation eats up 7 percent and income taxes on the interest eat up at least 1 or 2 percent, so the "saver" is lucky to break even on his savings. Real estate investments are a much profitable hedge against inflation.

DEAR BOB: Two years ago I rented my condominium apartment on a two-year lease, with option to renew for another year at the same rent. Since that time, property taxes and other costs went up. I'm not getting a fair return on my investment. Can I refuse to accept the tenant's option? Mrs. A., Alexandria.

DEAR MRS. A.: It was foolish, as you surely realize now, to give a two-year lease with a one-year renewal option without providing for any cost increase adjustment. That's why smart landlords provide for property tax and cost-of-living adjustments in leases longer than 12 months.

The fact that your return on investment is now poor is no legal reason to not honor the lease renewal. You took a business risk and lost. Consult your attorney to see if he or she can find a loophole in the lease. But don't get your hopes up.

DEAR BOB: We sold our old home and bought a more expensive replacement, thus deferring our profit tax. How long is the tax deferred? John W., Rockville.

DEAR JOHN: Your profit tax is postponed until you sell the replacement principal residence without buying another qualifying replacement.

You must defer paying the profit tax when selling one principal residence and buying another that costs more, if purchased within 18 months before or after the sale.

DEAR BOB: What's the best way to sell some Florida lots I bough for investment but no longer want to keep? Mrs. Lloyd S., Columbia.

DEAR MRS. LLOYD S.: Contact several realty agents who specialize in land sales near your lots. The local board of realtors can supply names. Ask the agents about their success selling similar lots, their fees, and anything else you want to know, including client references. Then list with the agent you feel will do the best marketing job. Be patient. Land sales can take six months or longer, especially if many lots are for sale nearby.

DEAR BOB: I took title to my home in joint tenancy with my sister. We've had a serious disagreement and I want her name off the deed. She won't sign a quit claim deed. As she contributed nothing financially to the home's acquisition, what can I do? Marie A., Herndon.

DEAR MARIE: Contact an attorney. It appears you made a gift of the joint tenancy interest; it may not be possible to force your sister to give it back. But a property partition sale may be possible. Your situation shows why joint tenancy, even with close relatives is not always wise.

DEAR BOB: How can I get a job as a property appraiser? F. L., Herndon.

DEAR F. L.: Most appraisers start by working for a bank, savings association, dependent fee appraiser, or country tax assessor as an appraiser trainee. Training courses are offered by the American Institute of Real Estate Appraisers and the Society of Real Estate Appraisers. Most community colleges also offer basic real estate appraisal courses. It is not easy finding beginning appraisal jobs, but appraisal can be a rewarding career.

DEAR BOB: In 1968 I bought a lot zoned for six apartments. A few years later the city rezoned the lot to three apartments. I recently sold the lot for $15,000 less than it would have brought if the zoning hadn't been changed. Can I add my $15,000 loss to my cost basis? Ernest B., Rockville.

DEAR ERNEST: No. Your profit is the difference between your adjusted sales price (gross sale price minus sales costs) and your adjusted cost basis (original cost plus improvements). The $15,000 "lost profit" has no tax effect. But your situation shows other readers the pitfalls of land investing. Ask your tax advisor for assistance, if needed.

DEAR BOB: I'm thinking of buying a rental house in Texas, where I plan to move in a few years.Would it be a good idea to buy now? Charles M., Chevy Chase.

DEAR CHARLES: No. Buy investment property near your present home so you can manage it properly. While Texas offers excellent investment opportunities, your home town probably has equally good possibilities. It would be extremely difficult to manage a rental house from far away.

The 13-chapter Bruss Report "Realty Tax Tips" is available for $1 sent to Robert J. Bruss, P. O. Box 6710, San Francisco, Calif. 94101.