Probably 8%+ mortgage interest at 40% down to make a safe assumption.

How to Price the Condos: Do a reverse amortization schedule for a 30-year mortgage based on Room Rental Prices in the Area.

Just make sure you’re comfortable with the interest rate if going either route.  

God forbid something happens and I either can't get rid of a tenant or can't find one, I would barely even be able to afford the mortgage

It's probably going to mean paying points at closing, a high rate, and a serious pre-payment penalty (like 5 years). 

My first mortgage was almost 11% and that was a good rate.

It worked out fine, though each time I got a little less than advertised interest rate (about 9% vs 10%) and I had to send a reminder email to to get my money back, but I did get it back.I ask about others' experience, because I'm still not 100% sure it's not a ponzi. 

Most seller's in a sub-to don't understand the risk they are taking and most lenders have concerns over the overall portfolio quality ratings which has an impact on their cost of funds.

I would be happy to go over some of the requirements for getting a mortgage in the US as an international investor. 

On insurance side of things, there is a lot of variables.