DEAR BOB: Why are real estate agents so intimidating? We just started looking for a home and have talked to several realty agents at weekend open houses. They are so discouraging. One said we can't afford to pay more than 25 percent of our income for mortgage payments. But it's virtually impossible to buy a house today unless the payments cost more than 25 percent of our gross income. It seems to me that the agents should encourage, not discourage, buyers -- Jo Ann G.

DEAR JO ANN: Most realty agents are anxious to help potential buyers purchase a home. Unfortunately, you got off to a bad start by talking to some negative-thinking agents. They won't make many sales that way.

Virtually every wage earner with a decent job can afford to buy a house or condominium. Your first home probably won't be your dream home in the best neighborhood, but it's important to buy now before home prices go higher

Stretch your budget so that you can afford the mortgage payments. Yes, they probably will exceed 25 percent of your gross income. I've seen many young buyers putting aside up to 40 percent of their income for housing payments. To keep your payments as low as possible, buy a home offered with seller financing so you won't have to get a new high interest rate mortgage.

Most homeowners will tell you that their first few years of ownership were rough. Making the monthly mortgage payments can be difficult. But as inflation raises your income, the percentage you spend on housing will drop.

House hunting isn't easy. But don't be discouraged. Work with a good realty agent who wants to find and help you finance a home. If you wait to buy until you think you can afford a home, you'll be waiting forever. You've got nothing to lose and everything to gain by buying a home now.

DEAR BOB: In July of 1980 we used that "residence replacement rule" to defer our profit tax when we sold our old home and bought a larger one. Now we have a chance to buy a better house for nothing down on a VA mortgage. The only thing holding us back is that we've been told we can't use this tax deferral rule again. Is this true? -- Charles A.

DEAR CHARLES: Not exactly. Internal Revenue Code section 1034, the residence replacement rule, cannot be used more often than once every 18 months unless the sale and replacement are part of a job location change qualifying for the moving expense deduction.

That means you will be eligible to use this tax rule again in January, 1982. Perhaps you can lease that new house until you are once again eligible. 1Then when you can close the purchase and get the tax deferral. Or you could buy it now and rent out your old home, thereby creating tax shelter benefits. Ask your tax adviser to explain further your alternatives.

DEAR BOB: All your articles on innovative realty finance are fine, but what about home sellers like us who need cash from the sale to buy another house? We need cash from our home sale so we can purchase a new home in Texas. Our home has been listed for sale about five months. How can we get cash from the sale? -- Dollie D.

DEAR DOLLIE: The reason your home hasn't sold is that most potential buyers can't qualify for a new mortgage at today's high interest rates. The solution is to sell your home the same way you should buy your next home, with seller financing.

In most communities you can sell your home for a 10 to 20 percent cash down payment, the buyer takes over your old mortgage and you carry back a second mortgage for the difference. Then buy your new home the same way. This is how homes are being sold and bought today, without new high cost mortgages.

Dear BOB: I am retiring from the military soon and would like to start a career as a real estate salesman. But I don't want to study to take an exam. Which states don't require such exams? -- Col. Thomas M.

DEAR COL. THOMAS M: All states require examinations for real estate salesperson and broker licenses. The necessary exam preparation will make you a better realty agent. For details, write to the real estate commissioner at the state capitol of the state where you want to sell real estate.

DEAR BOB: Our home is listed for sale. We recently received a purchase offer $14,000 below our asking price. (We know that our asking price is correctly set since we have based it on recent comparable nearby sales.) Since this offer was so far below our asking price, we refused to make a counteroffer. The buyer's agent got very mad at us. She said that the law requires us to make a counteroffer. So we did, but the buyer didn't accept it. I've wondered if we were really required to make that counteroffer? -- Hamilton A.

DEAR HAMILTON: No, there is no legal requirement that a seller make a counteroffer to an unacceptable purchase offer. However, it is normally done because realty agents know counteroffers often lead to successful sales.

The new Bruss Report, "How the New Installment Sales Law Can Increase Your Realty Profits," is now available. To obtain your copy, send a $2 check payable to "Newspaper-books" for Report 80109 to The Washington Post, P. O. Box 259, Norwood, N. J. 07648. Readers with questions should write Robert Bruss at Box 6710, San Francisco, Calif. 94101.