I have seen a few tiny home rural STRs that are really tricky to finance, even with a DSCR loan. 

We only have a tiny house as of now, but the infrastructure in place for a 5 bedroom dwelling.

Most people that I talk to about it give me strange looks when I tell them that we own rental properties but basically live in a tiny house (400sq ft RV) ourselves.Eventually, we'll go back to having our own brick and mortar house, but this season is actually pretty fun for us and we've really been enjoying it.

I would work with a rock solid STR agent in San Antonio to see what places are less strict as I know they have been cracking down.

I have heard Boise was cracking down on permitting, so make sure you can meet all licensing requirements and that you are in an area zoned for this type of use. 

Tiny homes are going to be a different clientele...

Additionally, the Airbnb market is pretty oversaturated here and a lot of the HOA's are cracking down big time.

In short, you need working windows, no cracking/chipping paint inside/outside, smoke and CO2 detectors inside, no overgrown greenery/trees outside, no holes in the walls, if you have carpet inside - it can't have stains or rips in it, and some other small stuff.

Wholesaler deals are better but the properties are tiny or the condition is so poor you have to flip it to make any money. 

Aside from the responses above regarding the bank likely requiring the 20% funds to be yours, good luck finding any private lender willing to take a second position note on a 100% LTV for any %, let alone a tiny 3%.Now, banks do, at times, allow seller carried back seconds, but unlikely with no skin in the game from the borrower.