Most won't though, and here's why: 1) you will be slower, 2) you will not be as skilled, even demo has a right and wrong way (I've had people cut a roof truss, then I have to call an engineer, etc) 3) you will be in the way, borrowing their tools, asking questions, etcBetter to just let them handle everything.... 

There is nothing wrong with EJ as a business model.

One wrong move, one wrong contractor, one wrong vendor…will erase any "benefit" one city has over another.

Eager to be corrected if I'm wrong here.

It sounds like they understand they're in the wrong and want to make things right.

For example: which option is most forgiving if assumptions are wrong — timeline, rehab scope, management, or even personal energy a year from now?

Those are things you can actually control.Your instinct about 1031 exchanging isn't wrong — but I'd suggest the issue isn't STRs as an asset class.

You could use a heloc to help with the new downpayment and have some reserves if something goes wrong. 

Prove me wrong. 

There is nothing wrong with have twice a month payments buy it should be written in the lease that way.