Building a home and borrowing 75k from family to do it. Tax implications and anything else?

I'm putting in about 70k and borrowing the rest for a total of about 145K to build a carriage house. My home in zoned for 2 residences, so I'll be living in the main house. I'm in Colorado.


I have no idea the tax implications for borrowing this much money. 


Should I have my family pay the contractor directly?


Should I form an LLC?


any input greatly appreciated.