Pulling Financing out of Cash Paid Property

[Abby Braaten]

I’m looking at some options for financing another property, this time a commercial 5-6 unit apartment/house. Currently I have my primary residence and a 4plex that's all rented out in Omaha. Parents paid cash at closing and I pay them back a mortgage each month (they wanted the interest income and I liked the smooth closing). No comments needed on this arrangement. 

Is there a way to pull that cash out and put it toward another property (with my parents approval of the whole situation)? Any other financing tricks?