An interdenominational Protestant church would accept anyone as a member if they claimed to believe the Apostles' Creed. Not all of them really did, but it wasn't enforced. Becoming an elder was fairly easy. The church constitution required twelve elders, and the church rarely ran over 100 in attendance. Almost anyone could be an elder if he wanted to.
The pastor told me that when liberals would try to seize the church and turn it away from God, the fundamentalist elders would usually quit the church because of the criticism they were getting.