Solving this now will help to avoid disputes in the future. Keep in mind though, it's common that these kinds of issues will turn off potential band mates. So, make sure they are in agreement and vested before forcing a contract on them.
Have it drafted by an unbiased third party (or take templates off the Internet). If one person writes it, it may seem like a power trip. If the members agree, you may choose a single person to write the contract, but have all members agree on the rules of the contract, and be in unanimous agreement before signing.
