DCF, JC and Greg hit it all on the head.
Take it from someone who tries to make a living rebuilding and repairing old cars:
If you're a one man band, you'll never get rich doing it. You will only have to work half-days tho'. It'll be up to you to decide which 12 hours you want to work.
If you're a large operation, be prepared to spend most, if not all, of your time making sure the business end of things are running smoothly. You won't have time to work on cars.
Restoring old cars sounds like a good gig, but the skill and knowledge requirements are astounding. You've got to know a whole lot about a whole lot, and that's just the cars. The office workload and dealing with customers can quickly take all the fun out of it. Employees (especially bad ones) can send you spinning.
It takes years to build a good reputation (if you're any good at it to begin with) and just one pissed off customer to tear it down.
I've been in business for six and a half years and I really have yet to see much of a return on my time and labour investment. We've got a very good rep, we're always busy, but I made more money working for someone else.
I could go on and on (and usually do

), but suffice it to say; there is a reason there are not many shops rebuilding or restoring old cars - most times the headaches outweigh the rewards.
If you've got your heart set on this tho', PM me with any questions you have. I'll give honest answers.