Cash flow for student rentals should typically be higher than normal, given there are more headaches to deal with along with more  wear and tear.

They will most likely tear up your property and be late paying rent with the most excuses!

Besides tearing the backyard up what other options do I have to remove these root so my tenant will not have a backed up basement?

Pace your self, remember to enjoy the bull ride, and laugh a lot along the way as there is bound to be tears as well, but not all would tears of joy. 

I would give them a notice to end the contract as soon as you are legal able to do so right after closing, and let them know that you will tear it up if they pay all rent due by the grace period. 

(Not surprising in our overpriced market.)We've decided to work with the tenant & have her child submit an application & we'll run the usual credit/background reports.I'm not thrilled to have 3 additional tenants because of added wear & tear.  

But, again, it's all about what your goals are for this investment, and how much time/energy/blood/sweat/tears you're willing to put in to make it work. 

He ended up tearing down and re-doing my bathroom which one of his subs screwed up.

Is there a market in your area for tear down properties?

I know you said you're looking for rehabs and tear downs, but where are you looking?