If the price is right and the parts are quality and you talk to the previous owner and know how he takes care of his cars then theres nothing wrong in buying a car already done up. Look at me. For the same price of a stock GTO, I got one that has been pampered and also has almost everything done to it that I would've done to a stock one. You just have to look everywhere to find those kind of deals and not get a ragged out one, ie: Phils 06 gto lulz. but srs though. scoure the internets and you will find a babied modified car for a good deal somewhere
or
Buy 5k roller and insert drivetrain of your choice