This is a fantastic story. What a great use of your talents and dedication!

I'm not sure what to think about going exclusive to one business (or chain). I'd be nervous about getting locked in so soon after discovering that you've got something to special to offer. On the other hand, the security of a regular paycheck would be nice...

In any case, don't sign any contracts without consulting with a lawyer! Something like this calls for real professional advice.

Congratulations on this new adventure!