Building bikes for a living could be done very easily if you've truely got the talent and one monster checkbook! The liability insurance and all the govenment licensings and requirements would be your biggest factors if you've got the talent. Getting all the government paperwork, doing it and getting your bikes in compliance will pretty much take a couple of years (most likely longer). Then you've got all the other stuff to make yourself a "legal' manufacturer of bikes. There's soo much more that I can't even begin to imagine what I don't know or haven't heard.
As Spincycle said,You should look into and talk to Sam at Firebikes, Rob at RHL. Also get in touch with Eric Hannan of Hannan Customs. Most of the old CBNers will remember Eric's horror stories along the way to his own company. Felt was heavily involved with motorcycle racing long before the bikes took off so he probably had the means to adapt easily into the bicycle industry. Also check with Brad from Atomic Zombies. He could easily start his own bike company but I think he's done his homework and felt that selling bike plans was the better way to go. Sometime check out the Basman's and how much time, effort and headache was involved for it to become a Legend among bikes, only to have Marcagi suck up the design!
I'm all for you or anyone else starting a legitimate bike company, but don't build inferior quality bike and sell them off to the unsuspecting public. And get the proper reqirements, licenses and insurance to protect everyone's butt that your bikes will come in contact with. Otherwise you and your bikes will eventually cripple the custom bike hobby and industry!
Good luck but be smart,
Chainsaw