Strangely, I have a similar situation. I own a rental property and the new prospective tenant wants her boyfriend to live with her without being named in the lease (she's going through a divorce). Am I setting myself up for a problem if she moves and he decides to stay?

I believe that if a tenant can prove long-term residency (via mail, CC statements, whatever) they are entitled to the same rights as a month-to-month renter. Can't provide a source now as I have got to run but try googling stuff like "NJ eviction proof of residency" or something along those lines, you'll probably be able to find it. Of course, if it's like, 10 people living in an apt that the lease says can have max of 4, then that's a violation of lease. So it depends on the exact situation.

I asked this of the Landlord Tenant office last year and was told people in an apartment not on the lease had no rights to stay if the leaseholder terminates the lease. But some people are telling me that's wrong, which would not surprise me. Does anyone have intel or experience with this?