legal agreement

I am composing a Classical string Quartet album of 10 pieces and am half way through the 8th piece. I do not have the resources to pay the musicians but hope that I can find people to join this project and receive part of any profits made. This would need to be written up in a legal agreement/ contract.

On the legal side I feel right out of my depth (as I usually do folk or alternative rock) and thus ask for advice.

My questions put simply are:

1. What legal steps do I need to take working with these musicians?

2. What percentage of any income should they be offered?

Thanks

Hutzpah

PS: I know you are not lawyers but just want to be pointed in the right direction.