My immediate reaction is apply the most you can to the (2) units today, to mitigate future capital expenditures.

I know nothing about them but await responses from those who do have reactions (good or bad).

It was an over reaction that really is not supported by the contract.

I got a similar reaction , I was told their company only made serious offers.

I've learned recently about longer term Interest Only loans, and ones that convert later to P&I payments, and may have an idea how to use them - I know, balloon payment bad, fixed rate good, but beyond that knee jerk reaction, please hear me out:My question is this: would it make sense to initially use a 15 year interest only loan to keep my monthly payments low, maximize cash flow, then refi in year 12 or so?

Their reaction?

The fact that your contractor signed that, is a huge red flag for me.If you dont want to fire him, talk to him ASAP about the delay money and see his reaction.  

That reaction and their ability to handle surprises will be the same for the duration of your relationship.  

It causes an over public reaction that gives us good eggs and bad name.

I'd have to think more about that, but my initial reaction is favorable.