I can't really give you any tips other than start building for your friends, If you still got any friends after 6 months then you must be doing it right
I've built a few for my friends and family and it gave me confidence, but never went any further with it.
Well yeah GeekSquad (at BestBuy) charges $40US just for installing one stick of RAM.
Danny, make sure you get some good refferals and stuff for your website/brochure