This is all made worse by the fact that there's no "collaborator" login (as other solutions have).

Some counties in Indiana would refer to this as an Accessory Dwelling Unit. 

I believe the best solution is for her to simply use the existing heater properly by keeping it on 24/7, as intended. ( which we already told her last year she has to keep her heat 24/7, and she say no way)Additionally, she habitually pays rent late.

Quote from @Carlos Ptriawan: Quote from @Scott Trench:The solution isn't to not passively invest.

Would love some actual reference to data if you have it (not anecdotal). 

We're wondering about various what-if's though, such as what if the people tear up the place, what if we don't want to rent to someone in particular due to references or credit or pets, etc.

I was involved in R&D program with O.C. on "solving" a solar-on-the-roof solution that (a) worked and (b) was scalable. 

I am definitely referring to a house that was already insured as a rental, not as a primary residence.

There are several topical solutions that can be applied to the dog to reduce fleas.

Can you put one on Houfy or similar site.You can always have one on YouTube and reference the link.