@Moises Acosta III I'm going to side with everyone else and say you need to start by contacting the housing authority to report these issues.

Unless there was something verifiably wrong with the tree AND you reported that fact to the neighbor and the local authorities, chances are the tree is YOUR problem, and not the neighbor’s.  

I would treat it as if your adding an authorized user to your personal credit card.

You'll have to contact your local housing authority and they can tell you how to get the process started

I’m a Nashville native, been in CRE for 5 years, and am the best selling author of “Open for Business: The Insider’s Guide to Leasing Commercial Real Estate.”Send me a message and we’ll get something on the books.

If everything checks out, I would refund their deposit (minus any damages you're authorized to recoup per state law) and move on with life.

Tenants are very much like sheep, and I have it on very good authority (Matthew 9:36) that Jesus really set the pattern here.

The taxing authority is not going to settle for less ... at this juncture.  

In the book "What Every Investor Needs to Know About Cash Flow" the author talks about not just vacancy but also factoring in rent that you can't collect for various reasons, for example a tenant who refuses to pay but is still living in the property (not technically a vacancy).

What was interesting is he's in the same niche but he's playing different markets...and it wasn't just the local economy,  but local conditions like aggressive taxing authorities taking a bite out of what is healthy revenues.