It's an invitation to come into the property and see how things are going, ask questions about their life, etc...

Special invitation and sell all units at once or if many condos, sell over a month. 

Thaddious Echols I invite you to please consider the following, from a Federal Income Tax Filing Perspective.

Discussing debt with anyone other than the person who owes you money is an open invitation to a lawsuit.

I would have a coffee with this neighbor (invite them over for a few minutes or something) if they are reasonable.  

I would set one or two open house times, and invite them to an open house showing.  

Every time you try to raise your rent you remind your tenant of how much they are actually paying and inviting them to question it's value. 

This must be taking a toll to on yours and her relationship.This is why I never, ever do business with family or friends.When things go downhill, now you have to deal with seeing them at company holiday dinners, ugghhhh.I am not familiar with the NY landlord-tenant laws but know that, should this be processed as an eviction, what you are doing currently whether or not it shows up in court is not right and legally could work against you.Trust me, I really do empathize with you and your situation and it seems like this Brother in Law is really taking advantage of you, but don’t correct this wrong with another.Follow the legal process to get him out, talk to your wife to see if she can intervene at all, but it seems he may not listen to her either and just does not care.So my laughter is because I cannot for the life of me see how someone can think that this kind of behavior is right to do to anyone, leave alone your family.This man/boy should be ashamed of himself for putting you and your wife/his sister through this mess.After this, I suggest you be very careful about inviting family over for those extended stays that never seem to end. 

You need to give formal notice to enter the property (aside from common areas) for any reason other than a emergency or having been invited in by your tenant.It is very common for tenants to ignore minor maintenance issue that will grow into huge repair expenses.

@Danny Johnson Requested an invitation for Flippilot.com looks very interesting!