As @Rhett Tullis mentioned, you really aren't left with a whole lot of margin on the deal either.

The rate is based on an index rate plus a margin - I don't know which index and I would have to back calculate to determine the cap interest rate.

There are 2 points to consider here:- Rising rates is good for banks (generally speaking) because it takes pressure off of the margin squeeze they've had to deal with for years. 

And it's my margin of safety if the market turns or I can't get it rented.

But even if it doesn’t, I only have $120,000 in it, so I have a margin of safety.

@Vincent CraneThanks for playing devils advocate.It is a thin margin indeed, my current goal is to pick up houses, that I at least break even on while managing myself (this house has the thinnest margin of any I own to date due to 100% borrowed money).

Transactional money might take too much of your profit margin.

Since the margins are typically so tight on commodity lumber, the supplier either has to take the hit and match the market, or ride it out.4) If you're including trusses in this, those can vary dramatically - huge swings in price... in part because the design is subject to the individual designer as well as some supplier have in-house truss capability while others act as a middleman.  

Your student loan debt is being serviced from after aftertax income, so that 6.8% needs to be adjusted for your marginal tax rate to yield what you must actually earn to service that debt (could be closer to 9-10% pre-tax).If you have forced appreciation in the house and it will appraise for 135K, you may be able to pull additional equity from the home to pay down (or pay off) your student debt ... effectively transferring your student loan (6.8%) to your mortgage (4.x%?).  

Ensure you profit is actually worth doing, lenders don't like thin profit margins as they end up with borrowers walking away.