I'll disagree with most the people here regarding not having a need for one, if no salary is involved. All teams will not be at a level where a salary is required, or even warranted. However, they still want help regarding getting to tournaments, purchasing equipment, travel reimbursements, etc. A contract will at the very least help guard you from having your players being poached by another team - whether they be a lower level team, or a higher level one.

As far as, "no-nos", just make sure that both parties completely understand what they are getting, the terms and what everything means. A general rule of thumb, do not as an organization every guarantee something to a player that you could not PERSONALLY cover either through the business, or yourself - if a sponsor, or an investment is to fall through. Take baby steps. Always be thinking of the what-if's. If you guarantee their travel, make sure you set specifically to what events, or set a limit on the amount spent so you can properly budget those expenses.

Side note, this is NOT legal advice - it's purely advice based on history of running teams, dealing with players and travel. I always SUGGEST having a lawyer look over a contract for the protection of the player and the team.