If the heads were in good shape and needed only a bit of valve work, and it was just the bottom end that needed work, and you did your own engine assembly then you could easily do it for $2k or less.....but that is a lot of IF's. The problem here is we don't know what you mean by 'properly done' and we don't have any detailed info on what was done to the engine you are looking at, or your abilities for engine work. So this is all only estimates and guesswork at this point.