+1 for [MENTION=185914]ClarkinHawaii[/MENTION] who gives good advice, IMHO about buying a truing stand. The initial cost will be a good investment if you want to build wheels. I use the one at the local bike co-op, but I don't plan on being a commercial wheel builder either.

There will always be a market for custom wheels, so I'd think that you'd have some potential work there. But I also agree with [MENTION=84476]cny-bikeman[/MENTION] that you need to be able to sell not just wheels but also advice. Your expertise and recommendations will be of equal value to your customers as the wheels themselves. So, in short, educate yourself in depth before marketing your wheels. Working with a local bike shop might be advantageous to both of you.

Best of luck!