I am cheap, but everything looks good and functions well- most important if you are renting it out. 

They are not going to get anything better than 5% even if they had a social as rates are above 5%. 

Here's a bit more in detail about how rates are calculated for DSCR loans:1.

If you're comfortable with a smaller percentage for expenses, change this part of the calculation - just realize you're ratcheting up your risk exposure on the property.Divide the net operating income by the prevailing interest rate (5%?

Also some lenders will offer this on newer originated loans.It’s not common but I have seen it offered on occasionIf there is a higher default interest rate then I would consider it but if it’s the same rate as default I would not accept it

with todays  rates , many  borrowers  wont  want to have their  1st mtg  rates   touched ?   

As I would have to move in at least for a year to assume that rate.

Is it Cash Flow, Cap Rate, COC, all three or something else?  

At a glance, it's just Quicken 2.0: advertise a great rate, bury in the small print over $10k in junk fees per $600k borrowed.

Here is what is being considered:SCENARIO 1):1) Parents loan us money at X% rate.2) Loan terms would allow for early payment without penalty (we would get a conventional loan in 2-5 years to pay parents back).