What would you do with $50,000 available for a second property?

[Mike Becher]

I bought my first duplex in August of last year (2018), which I currently have an $85,000 loan on through a local bank. I have a family member who is interested in loaning me $50,000 for a second property @ 8% interest for a 30yr loan with a 3-5 year balloon. First, what steps do I take to guarantee this is seen by the government as a loan and not a gift so we avoid taxes involved at the original transaction. Second... I'm interested in hearing about various ways to go about using that $50,000 the best way I can. 

Would love to hear your thoughts/opinions.