How "good" are you?

There is some work like building wheels that should be possible to do at home. Perhaps even contract out to some local bike shops.

There is, of course, buying and selling. There is a unique market of taking European products and dumping them on E-Bay in the USA. Or, taking European classic bikes, parting them out and selling on E-Bay.

You will have to really hustle if you wish to make something like a home bike job into a full-time business.