@Joshua Perelli so only a crazy person would accept being a LAIC for an owner self managing. 

If so, have them hold the builder to the fire, that is not acceptable for a brand new home and that should be on them to fix that and anything else.

Also, if you accepted full October rent, its unlikely you can claim they need to leave before the end of the month. 

Now, don’t get me wrong—I did accept the inspection report and signed the offer to purchase.

You just filled in and registered to the country clerk.Title companies won't accept to transfer the property without using a warranty deed, because they can't insure the title, but that will come when your parents sell the property and at that moment your parents will create a warranty deed to the new owners.

You'll either need to put more money down, or accept the reality that high leverage creates a higher debt service payment.

I’m not sure if I should accept the offer and roll my equity in a new property or just sit tight and see what happens?

Only way I will lock myself into 1 is if the exit fees are not prohibitive and % basis points is within acceptable ask price from the present lending rates, can surely go in for a higher deposit to tilt the balance towards positive cashflow i.e 25%-35%.

Secondly I just finished "Real Estate by the Numbers" also by Dave Meyer - even though I have a business degree and am actively involved in investing it was a really great refresher on not just the numbers and theories involved in real estate decisions but also the pros and cons of different return metrics and how all the metrics relate to one another. 

How could I structure a deal that would sound acceptable....