Because a FSBO apartment — that is, a "for sale by owner" — means sellers don't have a broker's commission to pay, they can often be good buys. Take Harris Firestone's two-bedroom at 150 East 61st Street, just off Lexington Avenue, which just went on the market last month. Though it's been renovated to the hilt — brand-new oak floors, crown moldings, totally new kitchen — its asking price, $1.095 million, is less than the average Manhattan apartment, and a little cheaper than similar units in the building and others nearby. Firestone, who consulted an appraiser before pricing his unit, says he has more room to negotiate since he's going it alone. "The large brokers charge 6 percent, which is absurd to me," he says. He'd rather pass on the savings to the right buyer. But the big test will be whether he manages to unload it at all. Brokers often say FSBO sellers wind up needing their services in the end when they discover they can't market their properties as widely as agents do. Maybe they're right — or maybe they're just jealous. —S. Jhoanna Robledo