What is the character of the sale of that partnership interest? 

If the initial attempt to reason and create rapport with the neighbor through neighborly conversation is unsuccessful, I'd consider sending a certified letter next so that it's on record, start the clock ticking on that if it does end up being an attorney situation, and make friends with the local code enforcement department officers. 

I recently went to a seminar regarding multi-family investing where they attempted to sell a $40,000 mentorship program.

I'm attempting to help out a friend's parents who are about to lose their home to back taxes.Is the process as simple as quit claiming the deed to me and then I pay the taxes and hold the property until they pay me back?

IN ADDITION once you do have the complaints in writing, section 'Disputes' in your agreement REQUIRES you to attempt to find a solution with the problem Tenant before escalating.

The local MF family is quite soft at the moment so I’ll keep trying to rent while I attempt to sell. 

Mold can be harmful, so gear up with a mask, gloves, and goggles before attempting any DIY.

But these are VERY rare occurances and one can spend years unsuccessfully attempting to conclude this type of transaction. 

I agree it can be hard but it does get easier with time and I like to think I'm a better judge of character as time progresses. 

Dont be surprised by high quotes... you don't always get what you pay for, but its a business they are going to attempt to sale you the kitchen sink.