eg if there is a bedroom downstairs, and only a half bath downstairs, then you should pay them to make it a full bath even they charge you an arm and a leg. because if it is concrete slab foundation, it is almost impossible to do it later. but the upstair bathroom, talk to a contractor about price of a remodel.
long time ago a friend of mine asked the builder not to put in carpet and saved a couple thousand, which he used to put in much better flooring after close.
