There is no background check to come to the Open House, or even to visit a Lodge. To become a member, however, Lodges do conduct an investigation to make sure that potential members are “men of good character”—one of the prerequisites of becoming a member.
Over the years, many scholars have commented that one of the reasons that Freemasonry has lasted as long as it has is because it has stayed out of the “rehabilitation” game—leaving that to the purvey of churches and state.
Masonry instead puts the focus on “making good men better.”