God decides who are the called out members of His family, we gather professing members of that body as members of our local assemblies. Some are tares, so we preach both to the lost and to the choir. I believe sometimes a "re-dedication" is actually an acknowledgement of salvation.
All this to say we should not be too persnickety with our "membership" criteria" for first time members. People coming from other churches, whether from a similar belief system or further afield, need to be in agreement with our "What we believe" statement. Unless physically unable, we require our members to be water baptized by full immersion. We also want them to make a public declaration of faith, and describe if possible, their changed life.
We offer a new members class, and a more rigorous discipleship program.
The real danger, in my opinion, is to tell someone, over the age of 12, that they must wait, rather than accept them just as they are! We are a hospital for sinners, and not just a hotel for saints.