@Leo GregoireTo answer your question directly about cash for keys:In rent-controlled states like California, you can sometimes pay 10 to 20 grand a door to get them out.I have never had to go this route before.

If the crime is so bad and the homeless is out of control along with the chickens, why is the rent still so high?? 

There are sometimes longer escrows, around 30-45 days, the pest inspection which you mentioned, and sometimes certain safety issues that need to be repaired.

Situation was beyond my control.  

@Heather FultzCondos can have the advantage of the maintenance of the outside taken care of but can run into issues with HOA and restrictions on STRs that you can't control. 

But if this is not the case one option would be to seller finance that way you can have control of how much income you are getting every year.

They are out of money or the banks are going to take control of the buildings and nothing is going to happen to them as they are getting their pound of flesh while the stakeholders are getting nothing.

Holdover tenancy is addressed by a significant rate increase for every day (I use 150% of market rent as that seems to be a reasonable enough number that a court would allow + costs associated with their refusal to leave) and I have wording that if I can't turn over the unit for any reason outside my control, I'm not liable. 

So, if the mess isn't going to attract pests like food waste and it isn't causing damage like pet urine then it may not be an issue worth letting yourself be bothered about. 5.

@Irving Vizcaino First I would use Mold Control by Concobium.