Newer construction code requires better earthquake-proofing, but it's still aimed at preventing a building collapse rather than holding the value of the structure.About 15 years ago there was all the talk about "100 year homes" but I haven't seen much come of that.

If you can find practice tests, that is my recommendation - that is what I did after taking the required time component and did not have any issues passing the test. 

ADU zone expansion is not certain, and even then who knows what the rules will be (owner-occupied requirement, etc).

Since you’re considering relocating, I can’t recommend the house hacking investing strategy enough.

In this case, correct, 1031 exchange is not available. 1031 exchange is property for property, and an interest in a partnership normally is not (with a few rare exceptions, so you may want someone knowledgeable to give you a second opinion for your particular situation, which requires reading your inheritance documents.)Whether or not you have any mitigation strategies totally depends on your specific situation and requires a one-on-one. 

Also since it's a 4-unit it would need to meet the sustainability requirement. 

I have purchased the following books:ABCs of Buying Rental Property The ABCs of Property Management The ABCs of Real Estate Investing The Advanced Guide to Real Estate InvestingThe Book on Investing in Real Estate with No (and Low) Money DownWhat order do you recommend reading them in?

Quote from @Pamela Rivas: Hi Natasha,Here are some key points to consider about setting up a Mexican corporation:Setup Costs: $1,500–$3,000 USDOngoing Costs: $1,000–$2,000 USD/year (accounting and tax filings)Benefits: Tax deductions for expenses like maintenance, repairs, and managementBest for: Multiple properties or income-generating investmentsWhile a corporation is ideal for managing multiple properties, it’s NOT required to obtain an RFC.

You'll have to meet higher ratio and FICO requirements. 

If so, I always recommend getting the study done prior to rehabbing.