Pastor, some reasonable considerations when considering prospective members:
1. If they joined and left multiple churches within a handful of years, your church likely won’t be any different.
2. If they speak disparagingly about prior church leaders to you, they will eventually speak the same about you.
Exceptions exist, of course. Sometimes they do come from bad churches with bad leaders.
But if you always think, “Yeah, but our church is different, and I’m different,” then you’ll probably deceive yourself into disappointment.
My point: prior to bringing them into membership, talk to their prior church(es). Kindly ask hard and challenging questions. Push into uncomfortable places.
If they don’t want to go there and leave, so be it. You may have guarded your church from painful conflict or discipline.
Better to detonate those grenades on this side of the membership process than a year or two or three on the other side when there’s a higher risk of shrapnel taking others out with them.