(would be easy to do because I have everything already in a spreadsheet)2) When do we actually pay this? 

It sounds as if you're not happy with the asset, the size, the unit mix, and its performance.You could wait until rates drop, and find someone willing to pay a higher price than now.

I have 6 rentals that break even and do not cash flow but help with depreciation but also plan to pay off in next 15 years.  

You could always have your parents draw up a contract for you to manage the property on an ongoing basis,and you pay them enough to cover their loan.

We do not recommend to any of our clients to pay points right now as the industry as a whole is anticipating rate cuts within the next 12-18 months.

Im willing to pay 75% of market value now to help you avoid the 50% crash, 

We’ve been good tenants paying on time for the entirety of our stay here.The property owners are brother & sister (and I believe a third sibling), but they’re never really on top of things, and no property management.

For my first property, is it A: better to pay cash and see how it cash flows or always use loans and save money for down payment and other investments?

We find that mom and dad are making sure their kid is paying since they're on the hook too. 

He gets an option to buy it for the remaining balance on the mortgage, and pays my mortgage down.Call it rent to own, or call it a loan with free rent as interest plus option to buy.Will it trigger due on sale?