I ran the numbers and came up with an offer price.

I've even got a contractor that will be available around the closing time for some of the bigger projects like moving the door, putting in windows...But when I ran the rental numbers they aren't great.

My issue is that I am finding it difficult to truly understand my tax liability and potential write-offs on an ongoing basis.

I ran my STR from Chicago for two years.  

Your lease should have a clause in it that requires tenants to promptly notify you of all water leaks - or you can charge them for damages.In this case, how did they NOT know about this ongoing water leak for the 2+ years they've been there?

My Dad and I are planning on going in on the deal together and he is willing to front a significant amount of capital for the down payment.

Your values above suggests you may be overlooking the ongoing gains made by the various investment vehicles during the continuing timeframe. 

As you will soon find, there is no common definition of a turnkey property, and it can be very risky (and expensive) to make any assumptions.The ongoing management of the property is another area of vastly different approaches to turnkey investments.

It's easy to obtain, costs very little, and doesn't require additional, on-going effort to maintain.

So I ran over there, eyeballed the rehab I would need to do on it and made a cash offer on the spot and they took it.