Do I simply need to write it on the purchase contract?

However, when we do our calculations, the property in Waco seems be more profitable in terms of cash flow.

I made a nice profit for SXSW this year by using Airbnb.

You would not need the additional income so would simply fold it back into your funds.   

Not familiar with your term, "house hacking" but I'd recommend picking a few ways to learn and profit from real estate.

With those type of tenants, and the age of the property...is it going to end up being an ongoing headache that will nickel and dime away the profits?

If you sold it can you break even on the sale or show any profit.

We didn't make any profit on the house but we did gain valuable experiences.  

With the potential of walking away with so much profit, we are debating whether it is short sided to change our plan from keeping it a rental or is it opportunistic to try to take advantage of a hot market with low inventory. 

For your bookkeeper you simply need to make a note on the invoice.