Do some brainstorming and see what other shop owners are offering. Is there any way that you could promote each other? Contact shop owner and offer a plan......don't just barge in and say "wanna collaborate?" Make sure you've given it serious thought, write down ideas and then have a short term plan in hand to offer. I think a good way to start is to give it 3-6 months and then if the other party wants out......no problem. As Mark said "be on even level and ask for HONEST thoughts", otherwise you're headed for disaster. Honesty IS the best policy.