People responded by explaining that residential mortgage lenders are looking for US-based customers, who have their residence, income and assets in the States.How do they view foreign debt?

Living in one unit and renting out the other helps you scale quickly because you need a lower down payment for a primary residence. 

We had 4 yrs of college, 4 yrs of medical schools, 6 yrs of residency, 2 yrs of fellowship.

But a bedroom or a bathroom can be easily qualified in terms of dollars (I usually see $4,000-$5,000 allotted for differences in bed/bath count).Truthfully, if I can't find easy comps and if I can't make it easy for the appraiser to agree with the value I'm looking for, I just don't buy it.

A house hack for a primary residence for about two years and then you could repeat this again. 

If married you can exclude $250,000 each in capital gains if your primary residence.  

Well, 30K I loaned myself to buy a house which is now my principle residence.

My primary residence is in a trust.  

is that it typically comes with higher rates on the first mortgage, if you're low income enough you might qualify for near free DPA but most DPA's open to all income brackets are typically at higher than market interest rates.

Investment Info:Single-family residence fix & flip investment.