PLEASE, PLEASE, PLEASE BE VERY CAREFUL!!
Try to get to know someone before you go into business with them.

I am talking from experience. I got totally fuked over after going into business with someone I hardly knew.
I'm still paying business rates off now and the business ended in Aug 2010!

Talk to a solicitor and get some dam good legal advice first and do it by the book.
Try and protect yourself as much as possible mate.