Also, not very easy to use typical methods of valuation like comparable sales - there is no public tax assessor's website that you can just freely grab this from. 

It can be a bit of a juggling act, but it’s a method some investors use to grow their portfolio without waiting years for equity to build.I guess what I'm saying is, it's not just about waiting.. it's about finding creative ways to leverage what you already have.

I use their payment method and they deposit into my account and it's very simple.

What are the best methods to independently verify zoning and land use data to ensure compliance with local regulations?

We moved plumbing, adding electrical, and added new appliances in the kitchen. 

And while nothing is foolproof the most consistent method of finding good vendors is relying on OTHER real estate investors that have worked with those vendors. 

Possibly already permitted outbuildings that already have plumbing such as workshops, offices, etc might be able to be converted to an ADU at a cost that does not result in the cost being more than the value added.Building an ADU is a lot of work and can be a slow process.  

, status of major building components (roof, HVAC, structural, electrical, plumbing), accounts receivable aging (are all tenants paying or is the $20,500 schedule rent?)

Are there any particular investing strategies or methods you’re leaning toward?

Permits are basically only pulled for electrical and plumbing of if they get caught.. its the only way to make the rental houses cash flow in many of those markets.On top of that licened contractors many times simply wont work on those type of properties there is no money in it for them..