I anticipate that the no-seasoning DSCR will soon accommodate STR.

This listing is an active STR and I will be blocking the date starting on 12/1/23, and of course I don't want to turn down any rent slots in anticipation of getting STR bookings. 

All you need to show is that the rental income covers the anticipated mortgage payment.

My worries are liability, their ability to pay rent ( since they are not employed and I think they are anticipating income from this business) and their lack of prior experience ( which I think would lead to potential unnecessary issues if any).

Listen, this is clearly a money pit and the first rule of rehabbing, in my honest opinion, is that projects COULD take longer and MAY COST more than anticipated.

If you don't anticipate any vacancy, don't include vacancy.

I would be surprised if any new construction would be open to seller financing as I have never seen that before.You should anticipate paying 10-30% down in today's market for the numbers to start to make financial sense for your investment. 

To me this signals the investors don't anticipate servicing the loans long-term. 

Next year, everyone is anticipating that interest rates will be lower (election year, possible recession, etc.).

I am not anticipating a good couple of years for Texas and Florida investors, and parts of CA can absolutely be included in that.