The first pillar is avoiding unnecessary and risky activities (don't drink and drive, insurance generally won’t cover your poor decisions) and take good care of your investments - these simple steps will help you prevent lawsuits before they even occur.

Kick them out asap to prevent further problems.

What’s the best way to prevent this from happening to you as a wholesaler?

Monthly fees, maintenance fees, monthly reporting, tenant screening, preventative maintenance, timely billing... it's not easy to find a company that will take care of your baby and spend your money like it's theirs.  

This is the chance for current tenants to point out things that are broken (a fresh start for them, unless seller has a checklist at move in), and this gives you a chance to show the condition of the unit upon purchase and prevent further damage that you will end up paying. 

. :) HOAs cannot legally prevent a homeowner going solar.

I like to go to the California Association of Realtors and buy their forms to use, it can prevent a lot of problems, and if you go to court over something using their forms will only work to your advantage.also, I always try to get a pest inspection before I buy if I can, because your going to need one to sell the house.

I can imagine from time to time you'd have to wait a bit to pay down the helocs in order to reuse them again but I believe it prevents the issue with getting mortgages. 

I don't recall the exact language right now and I don't know what would have happened if I ever got into the situation of having to enforce it in court, but the lease option contract that my lawyer created for me has some verbage about situations that would prevent the lessor from being available at the time of closing on the purchase - such as incarceration or death.

My purchase option just prevents them from selling to someone else during that time and locks in my price when I do purchase.