Hello, Problem is this: My 70 year old mom owns a mobile home in upstate New York. She rents to my niece. Niece pays rent, but has a boyfriend live there. No lease between anyone. Boyfriend needs to go. Is abusive. Drinks, screams all day long, fights with all the neighbors, police called up to 4 times a day. Boyfriend has broken out windows on home and cars. Boyfriend has no rent receipts and is not on my mom lease with mobile home park. Is he consider a tenant? How can we get him out

He is a guest he has a live in arrangement with niece.
I doubt, ( but heck my night to be wrong) but you can't get rid of him without evicting niece as well. If the niece tells him to leave, you can make him leave.

So if boyfriend has damages all that property why is he not in jail ?

But in general, unless the lease limits who can live there, she can sublease or have room mates herself, time for an attorney, but be ready to evict niece along with boyfriend