Private lender plus conventional mortage

[Jeremy Stroud]

I've closed two deals in the last month. One duplex and one 4 plex. I expect both to cash flow positive from the start and end up with nice returns. 

If I continue buying at this pace I'll certainly run out of money for the 20% down payments at some point!

One option I have is to take an interest only loan for the down payment from friends or family at 6% with a return of principal to them at a certain point in time. Maybe 2 years or so. 

I'm having difficulty figuring out how that second loan impacts my cash on cash return and total return.

I'm looking for some helpful advice!

This is my last deal if it's helpful to have real numbers. How would It effect return if I borrowed the $35k for down payment with an interest only loan at 6% with a balloon payment due at the end of 24 months