After we started building we found that our neighbor’s house was 3 ft away from their lot line and they needed to buy 7 ft of our land to meet the city mandated 10 ft setback.

The state does not mandate that the ADUs be at an owner occupied property but both local cities (San Diego and Escondido) that I have looked into does mandate that the owner occupy either the primary unit or the ADU unit. 

However, I saw in my community that some housing development doesn't seem to match the regulations mandated by the city.

Having or not having income and net worth is a choice that people make...it's not a government mandate nor is it predetermined at birth. 

For instance,When the market crashed, the banks had too much debt and the FDIC mandated selling the notes and/or foreclosing on the homes before they would have more cash available to lend.

Why not take a couple days to create a small team of contacts you mandate to be used for all repairs?

I just read an article, which is not in English so I am not sharing, that the Parliament in Portugal mandated that landlords cannot evict elderly (65+) and/or handicapped  if they'd been renting the same dwelling for 15 years or more.

A Loan Estimate (must be that verbiage exactly) is a federal mandated form that lenders are required to show your loan on. 

Mandate proof of liability insurance by the tenant in case the animal bites someone. 

This is obviously an FHA loan and FHA guidelines mandate you living in one of the units.