maybe they would do a subject to and have you take over their mortgage payments - do they have a good interest rate? 

Quote from @Jaren Taylor: Quote from @Chris Mason: If you have the ability to market and raise money, then you secure the down payment, and do the normal commercial mortgage process. 

Lenders are also usually using your middle mortgage FICO credit score. 

Buying at the mortgage balance (~$150K) positions is under the fair market value and can trigger gift tax rules.

The cashflow should cove ALL of the expenses for the primary (mortgage, taxes, insurance, utilities, etc) AND put money in their pocket.

Mortgage- PITI2.

Insurance proceeds are typically provided in a check that must be endorsed by both the policy holder and the mortgage holder. 

I own a mortgage company, so I have my loan officers use this Fannie Mae income calculation tool for all business for self borrowers: https://singlefamily.fanniemae.com/applications-technology/income-calculator .

For example, I've used several banks for loans: Flagstar Bank, All Western Mortgage (a broker), PenFed Credit Union (HELOC), NewRez and probably a couple others I'm forgetting.

- very low remaining mortgage balance!!