What would you do 133k heloc 50k cash

[Gary Love]

We have a duplex that cash flows about $1600 in the Columbus, OH area. We have 133k Heloc available and 50k cash.  For the more experienced investors what would you do if you were in our situation? Looking for more long term hold but open to suggestions.  Just want to make this money make a difference for our future and retirement in about 15 years or so. We appreciate any and all advice. Thank you. Have a great weekend!!!