Of course if you want to switch to different license type, you have to go through the whole application process again, and pay applicable fees.I believe this is governed by the accessory dwelling unit ordinance which was revised recently. 

How likely is the local government to honor a 70 year old variance?

As I'm sure you know energy has never been an open market, every form of energy receives significant government support, and solar is no different in that regard. 

They were very credible, yet had no mortgage or rental history. 

I understand this is some type of federal government assistance program for low income areas.

Bonus points for more recession proof industries (health care, government jobs, education)Median income over $40k (your tenants need to be able to pay the rent)Average home price over $100kLow unemployment rateLow housing vacancy rateMarket with a strong affordability factorLandlord friendly  Those are just some examples. 

Without substantial government subsidies, tax breaks, etc. the numbers just don't work.There's a saying among RE investors who deal with large apartment complexes: "If you want a C-class property, build an A and wait 30 years."

If a tenant is receiving government assistance (Section 8, Abode, Vash, etc.) then they are NOT restricted to rent control. 

Luckily we sold the property to a buyer who was desperate to get into this particular complex and was receiving grant money from our state government to cover her down payment.

I don't know anything about real flow.I do know that 8 out of 10 cases there is an investor carrot site ranking in the top 3 positions on GOogle.With a bit of Jerryll SEO, this will happen:and these leads are SUPER motivated leads, for free organically.If you are serious about it, and realize it is not  (just) a magic website... you NEED to work on credibility and SEO...