I did as Squiz suggested last year - not in the bike business, but agri engineering and weld/fab etc. Work full time 8.30 till 5.00 for a manufacturing company, then out around the farms evenings and weekends.
Doing it that way I didn't have to borrow from the banks so I don't owe anybody anything. If things go down the pan with the business, they won't be able to take my house away.
It's hard work doing the hours, but I get more satisfaction out of it than any job i've ever had, and it pays for those little extras like resoring a 45.
I don't think I would want to go full-time self employed (but that's just me and my opinion) but I know that if my day job goes squit I can still pay my mortgage, and some of my customers have already said that they could find me a day a week permanent if I ever need it. Only takes five of those ...
I don't know the bike business well enough to make recommendations, the above is my own personal experience and at the moment i don't regret it.
Which ever way you decide to go, good luck with it.