I'd lean more toward 6 months unless the person is just completely new to Hive, and then I'd say 12 months.

It's probably easiest to just bring it up for discussion at the end of whatever period and whenever a new member is inducted, and just say, "X person's scholarship is expiring. Does anyone want to renew it? Y person is a new member. Does anyone wish to sponsor them?"

There'd still probably have to be a sheet but it would be much simpler if it's just one to one only.