Many opt for other investing methods in their SDIRA like private lending, crypto, private equity...anything except collectibles and life insurance.Note that a Solo 401k is exempt from UBIT on leveraged real estate so if you have self employment activity and no full time employees save for you and your spouse you should consider the Solo K as an option. 

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. 

I have other money that'll cost me 10%.

There are also people who swear by one method or another.   

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

It’s also important to be as specific as possible in the scope of work for each line item—clear details can save you from misunderstandings or unexpected costs later on.I specialize in consulting services for situations just like this, helping clients work confidently with contractors by bridging the knowledge gap.

What's the highest success percentage method to find a previous tenant's new address for this? 

I would consider staying with your parents and investing in another market that stretches your dollar and covers the cost of a professional property manager.

I don't expect to know everything by then, but I hope to develop a basic strategy that prevents me from making the most common and costly mistakes that a newbie can make.

Each lender can use their own methods of qualification on commercial properties, and most look mostly at the asset (with the exception of your FICO, experience level and reserves).