I'd prefer to focus initially on cash flow to supplement current income. 

My goal is to own as many rental properties as possible so I can hopefully retire young and supplement my income through rental properties.

If yes, that's going to require a far different strategy than if you just want a few nicely located homes that will appreciate over the years to supplement your day job income and/or retirement.Be sure to include timeline too. 

My short term goal is to supplement part of my income so I can assist my fiancé with some of her grad school payments (she is about to start PA school in January).I think I am only looking for some experience to understand what to look for, but I would like to have a couple of toes in the water around the start of the new year.

I rent out the tiny house to supplement the mortgage on the main house in which I live with my family.

Essentially, we would like to supplement an income (my mother's) which is approximately $24,000 after taxes.

Really looking to supplement my current income with some passive income from SFH. 

That's another reason I am now supplementing my Bay Area rentals by investing out of state in a more landlord friendly area. 

I am normally aligned with your thoughts but we may be misaligned on this one.Offering packages may say 5 or more years for conservative purposes but many have plans to sell or refinance (supplemental loan) after the value add to realize the sponsor compensation on the sale, eliminate/reduce the preferred return, and to maximize IRR and increase the velocity of capital. 

The most modern units have resistive electric elements to supplement.