@Matthew McCarty and @Aileen OuyangInvesting in anything is specific to each individual's goals.

This is a touchy subject.If you observed specific concerning behaviors during interactions, such as rudeness, aggression, or disrespect for property, these could potentially be valid reasons for rejection if documented properly.You should add one very important things to do on your checklist, past landlord references and it must be legit and find out why they aren't there any longer.

With all of that in mind, I think it would really be dependent on where you see that specific market going.

Rent control laws are market specific.

Part of this is regulations in my city, but after having done it this way, I wouldn't ever want to do it with a single family home.

This five-year expectation has become the industry norm.

Assumptions: specifically allowed in city ordinances, mobile home manufacturing in the area, or that someone heavily marketed that area as a retirement location in the past. 

I don't care for Section 8 investing as a specific strategy.

How specifically could they have done that?

Call the zoning department again, and this time ask specific questions: Is a variance required, or can you proceed as-is?