The first time Danny Bonaduce saw this brownstone at 654 Washington Street, in 1998, he made an offer -- I think I love you! -- before even getting to the second floor. Which he promptly renovated, adding miles of wraparound mahogany bookcases. (Who knew? Danny reads!) But the Partridge Family moppet turned junkie turned D.J. recently took a new gig in Los Angeles and last week sold the house for a surprisingly modest $1.85 million. "A renovated single-family for under $2 million? I've never seen anything like it," says MLBKaye International's Warren Pearl, his broker. The buyer, a Wall Street investment banker, looked at 30 other places before reportedly falling for this place as fast as Danny did. (He's keeping the bookcases but gutting a lot of the rest of the house.) And Danny got his asking price -- meaning all concerned could c'mon-get-happy.