My main concern is whether it's hard to meet their criteria for properties and secure funding.

Without getting into the weeds on the point of view arguments and everything between you and the seller, the main take away here is that the seller doesn't want to sign your mutual release.

I’m mainly concerned about the rate change happening without prior notice, especially since both loans started and are closing on the same day.I’m scheduled to sign tomorrow and close on Friday.

As mentioned the main downside to using a SDIRA to purchase properties is you get no tax benefit upside (depreciation) and have to pay taxes on UDFI.

To make the job flow easier, but also (mainly) to protect myself if a customer changed their mind later ( which was common).

As you know, I'm probably the main proponent of the great investment opportunities Mexico offers on this site and I will help and support anyone who wants to take advantage of these great opportunities.

Mainly how or if you offer them at your STR.

The fact its in a landbank tells me that it was taken back for some reason, which tells me its likely not a high commercial demand for development, but I could be wrong.If it is "on the main drag" in this town then I'd think doing a new build home to do a targeted and intentional air bnb would be the best bet. 

My main focus is Class B and maybe some C+ properties around NE Columbus, as well as outside 270 from the North to the east side.

One main regulation I find in Ontario Residencial Tenancy Act section 134 (3) states you cannot make a profit in subletting.