To answer one question before you launch: will this raffle actually raise funds, and how much? A budget helps you spot a raffle that costs too much to run before you commit time and resources.
Any prizes you purchase, printing and promotion, platform and payment processing fees, and other running costs. Small, unbudgeted costs are how margins leak.
One you could defend out loud. For a community organization with a decent prize, converting 10 to 20% of a warm audience is solid.