yes - my son does.
He started out when he was 22 and still lived at home, so that kept his costs down
After a year he opened up a small shop in Paisley (Scotland) to take in repairs and also to act as a workshop
He also sells reconditioned towers, laptops, cables,filters and various accessories
He buys job lots from Ebay, repairs and upgrades them and sells them on
He doesn't sell new p.c.'s as that would cost a lot and there's too much competition in that market.
He has various large contracts now for repairs, web design and updates
He does domestic and Businesses and makes a good living
He isn't formally qualified either also he did some college courses, but learned the rest by online tutorials and sheer hard work. He's 27 now .
Don't know if I'm allowed to give his website on here, but I will anyway as it helps to answer your question