A 20-year-old man who was a licensed real estate agent was indicted yesterday by an Arlington grand jury on a grand larceny charge in what police described as an elaborate scheme to sell a fake second mortgage on the house of an unsuspecting couple.

Robert M. Pasicov, a student at Old Dominion University who lives at 7722 Crossover Dr., McLean, was arrested Jan. 7 when he went to pick up a check for $8,250 from an Arlington mortgage company as payment for a phony $12,000 second mortgage, according to Arlington police.

An employe of the company had called police after routinely checking with the owners of the supposedly mortgaged home, Mr. and Mrs. Lawrence K. Donovan, and learning that they had not taken out a second mortgage, according to Arlington Detective James P. Griswold.

Griswold said that, as a licensed real estate agent, Pasicov had access to a regional computer bank of information on homes for sale.

The Donovans had put their house at 8709 Prudence Dr., Annandale, on the market, so its computer listing would have shown that there was no second mortgage on it, Griswold said.

The detective alleged that the phony second mortgage was filed in the Fairfax County Circuit Court in an apparent effort to give it legitimacy.

The alleged scheme was discovered when Earl Lovell, an agent of the Hansen Mortgage Co., called the Donovans seeking information about their house for insurance purposes, Griswold said.

If convicted of grand larceny, Pasicov could be sentenced to up to 20 years in prison.