The property fell in my lap at a really attractive price and I thought I would be fool not to try and pursue it further by utilizing my network. 

If it is a great property that will cash flow well you can delay putting in new windows for a bit and then with the extra cash flow have to ability to pay for the windows in a pretty short time frame.

I am a real estate investor, short term rentals (Airbnb), and looking to acquire additional properties in the near term. 

Also, you should look for opportunities to buy below market and force some appreciation, so that you are not 100% dependent on cash flow to make all your returns, you will be insulated to some degree from short term market fluctuations, you create multiple profitable exit strategies for yourself, and your cash flow numbers should also improve to boot.

In short, I don't have much.

If sub 10 years and you want to sell the cap rate starts rising because buyer cannot get good loan terms from lender and must buy cash or put a lot down with a short amortization schedule.6 cap for franchisee is not good.

The unit rent is likely to go up in the short term increasing the cash flow. 

Its been my experience that most contractors aren't fun to deal with under normal circumstances, but if they even suspect they will get shorted, you're almost guaranteed that they'll stop work immediately and you will face this exact same situation again. 

The SoCal guy said, "you're never going to lose if you find a deal and keep it for the long term, don't focus so much on short term fluctuations."

Books, short seminars (don't buy into the upsales), BP membership...stuff like that.