id just build the computer and have it up and running for 2-3 days to make sure nothing happens, then sell it to the customer AS IS, i mean if something goes wrong and they call you up saying, hey there is no video on my monitor? and you think it may just be a bad video card/monitor, that you know you can still RMA, tell them, hey i did sell you this computer as is, BUT this is what i can do, and tell them you can send it back for a new one, and you can either tell them youll take it out, they pay for all shipping expenses and you can either reinstall it for free or charge them a small fee, make sure if you do this to have everything in writing, like jeff said, there are some people out there that think if they drop the computer and it breaks then its your fault for making it.. ive been told its a hard business to get into but make sure you have everything together and contracts made, before you start putting it in the paper, who knows, 10 people might see that ad and want a computer built for them in the first couple weeks. good thing about if you sale someone a computer they will most likely come back to you for repairs, virus and spyware removal, which would also be profit. or heck why not offer free upgrades/virus removal to people if they buy a computer from you, give them a card or something that gives them free for 6 months or year, ya know.. that would kinda get you cusomters.