@Jay Hinrichs yes Maui did the same thing after the Lahaina fire, and you're also right that Santa Rosa had no such restrictions. 

A good safe rule of thumb is half of a studio apartment but this is not a hard rule.

The seller has the two lots legally separated, but due to deed restriction imposed by the subdivision development, found that building a house on the “tennis court” lot was not allowable. 

I use the individual stackable units when I have space restrictions.

Do any of the tenants have Dogs (Breed restrictions are individual to each company).These may not prevent you from getting insurance but they may limit the number of companies willing to insure it.

Lots of cities have restrictions..Arlington limits to a fairly small area of town, Ft.

Self-Directed IRAs (SDIRA) or Solo 401(k)s allow tax-deferred or tax-free real estate investing, though they come with IRS restrictions.

I did do a precursory investigation into what requirements are and it looks like there might be some zoning restrictions, as well as permits required.

I have heard there are FHA construction loans but that they are pretty restrictive and do not allow for multi unit construction.

It is just the IRS rules.