You can use an attorney or a simple partnership form (available at stationery stores and online) to draw up a binding agreement that covers potential problems and their solutions. The agreement can answer who owns what, who pays for what, when they pay, how shares can be sold without dissolving the partnership (if at all), how to handle disagreements, and what to do if a partner falls behind in sharing costs.
Stall Warning!Before you sign any legal document that binds you financially, consider hiring an attorney to help you decipher your rights and obligations. A few hundred dollars might save you thousands.
If a flying partnership sounds like a good option for you, delve into it further through the Aircraft Owners and Pilots Association (AOPA), Experimental Aircraft Association (EAA), or by reading aircraft partnership books available through FlyingBookclub.com.