We have a family here that claims to be missionary's from Germany, living on an Indian Rez, not paying taxes, claiming a building on their property to be a church. This Church has not grown to beyond 12-14 people since they came around 2002-2003, they don't hold church in this building. They appear very shady, and claim to have a green card / visa, how do I check them out to find out if they are legit? This church isn't open to just anyone, only by invite, my son has been sucked up by this "Church" and they have been influencing him and pulling him away from his family. I really need to check them out. Plus my son has given away 3 vehicles and furniture, not to mention several thousands of dollars over the past 3 1/2 years.

While not a good place

A church does not have to have more than 2 or 3 members to be a legal church.

A church does not have to be Inc by your state to be a legal church.

A church is tax exmept by being a church, having a regular metting place and members.

A church does not have to be open to everyone,

Now this really sounds like a cult, that merely sucks young people into it,
I hate them, they are evil, but may not be illegal.

Have you discussed this with the local police

Sounds like a cult to me...