Small Claims Court is also good, pro is you get an enforceable judgement so if anything is unclear such as damages amount that will be determined, cons are time and expense involved and once you win the big challenge is enforcing the order.  

That's how you win their hearts and make them see you as the ultimate investment partner.

Sure you might lose on some listings but you will win listings.

The easiest way that I have found over the years is to simply ask other investors, specifically in your local market.

The company that serves and blessed me over and over again is what you would call a Tax Advisor, not simply a CPA or tax preparer. 

Unfortunately having title issues is one of the reasons that sellers are sometimes willing to do seller financing simply because they know mortgage companies won't approve without proper title work and title insurance so they have to be more creative in the ways they sell but that can be risky for you as a buyer.If you do seller finance I recommend having very specific terms on HOW payments will be made and accepted and using a professional service like https://www.agecroftcapital.com/ for loan management in the case of any disputes - just my personal rec, not sponsored by BP though I do work for BP :)

If done right, it could be a win-win for everyone involved.

Is there a business you can simply push up and increase revenue by a lot to produce the money you want to invest? 

After 5 years and very little progress on the ADU valuations I suspect the ADUs simply do not have a value equal to the small unit, small count cost and never will.  

I'd simply let them know that you are not going to renew their lease.