. $4500 seems like A LOT of money to transfer our digital plans into CAD (the contractor already built-out our design ideas on his laptop's software) and have an engineer ensure we're using the right beams in the right places.

In China it is a product of currency control.  

Time is your currency, so put it to work.  

Unless you can provide your private lender with secured double digit returns, I agree with most, your dad may have to do this on his own, or simply have you intern with him on this deal. 

Personally I would invest in a fund with an 8%+ preferred return with equity split that pushes the realized return to double digits before I would pay off that debt.

I know of a few funds that offer preferred returns, and project double digit returns in total.

Currently I add the guest's last 4 digits to the locks as a code remotely a few days before their check-ins.

A lot of design questions can easily be answered with pictures and digital correspondence. 

About 500 posts a minute of people that never make it into the double digits on their posts counter.

We are able to get double digit returns with very a passive investment.