Just a sidenote: One such detail is the timeframe... I am my own boss and I love to do contract work, but I cannot say "Yes, I will do this", commit to it and then after months the money is raised and I am drowning in projects.
Perhaps the money can be pledged and held in escrow either until someone accepts the work for scheduling or it gets withdrawn by the pledgee due to inaction.
Truly a tricky spot. Who keeps an eye on the features for things like code quality / deliverables? I don't know how I would solve this, yet.