If for some reason they can't get this sorted out by the next payment date, you should figure out how to physically escrow that payment somewhere...this at least protects your payment until you're confident who it is supposed to go to in the future. 

Have since insured a triplex with them as well, saving several hundred dollars in the process.

@Marc Zak Using an LLC for each property provides strong liability protection by isolating risks to individual assets, with income and expenses flowing through to your personal taxes on Schedule E.

That complicates enough I'd consult with an entity/asset protection pro.I don't hold residential assets in LLCs unless partners got involved. 

Roadside Tree Protection Plan.I was told I will also have to get  stamped and sealed architectural plans of the 6 unit building.

You know much more about Vegas than I do, but winters are colder here and summers are cooler as well.

While you can start with a written agreement, a professional document will help protect both of you, particularly in terms of ownership, responsibilities, and profit-sharing.

All well and good.

Seller should record their lien against the property, you both should have an attorney review to make sure all interests are property documented and protected, and i think everyone is in a good place. as far as evicting tenants... this is up to what you and the seller can negotiate. i would still be putting on the same contingencies - appraisal, inspection... know what you're buying. don't get blinded by the seller-finance piece. 

So, I would be very conservative (for your standpoint) on the researched estimate.I would do what I suggested above, then if the tenant takes you to small claims court you explain to the judge the legislative time restrictions you were under in order to come up with an accurate repair expense.This is yet another example of how "tenant protection" laws, in practice, end up hurting the tenant in the end.