I agree....As long he is not interfering and/or tampering with your mail he is not doing anything wrong. The PO box is a great idea.

Would this person be protected from litigation under the Good Samaritan law?

As stated more information is needed to correctly asses and answer your question.

How do I protect a real estate investment ( a condo) and keep it for my disabled son from a possible financial liability?

Agreed, please post to the correct practice area. You can use AVVO to locate a qualified attorney to help you in this matter.

How do you think Small Claims Judges feel about activism / advocacy groups in landlord / tenant disputes? ?

Agreed, judges want to see parties come up with amicable settlements and do not put much thought as to what groups you are associated with.

I moved sept, 1st and still have not received my $500 deposit. can I take her to court to get it back?

Yes you can. Ask her for a statement if the damages and go from there. If she does not return the deposit you can sue in small claims and she...

I agree they should have told you what their reasoning was to be there. Take this up with your counsel if this proceeds further.

What's my risk for and how to avoid a DUI?

As stated I would secure counsel as soon as possible to handle this matter.

My my son was involved in a car accident 3 years ago over a little over 3 years ago and now their insurance is wanting to sue us

As stated this is one of the reason you pay insurance. Call your insurance company and turn it over to them.

Am I required to provide an additional 10 day payment window to a late rent once I've implemented the late fee?

Most basic answer......What is stated in the lease? Do yo have a written lease with the tenant or is it all oral?

Will we be able to renew our lease?

As stated the landlord can refuse to renew your lease for no apparent reason and you have no recourse.