Avoid putting in cheap items and put in more durable - tile vs carpet, mini blinds vs faux wood, lights instead of ceiling fans.

The seller countered, explaining that they had installed a new AC unit and made other updates and they would not consider going any lower. 

You might have to pay to keep these installed.

What type of floors did the contractor install? 

To make the most possible you will want it to be nice and inviting, also have a shower installed and at least a kitchenette IMO.Once you have your total cost for build out and furnishing, then figure out projected income. 

The quote includes the HVAC machine and installation.

I understand that you have to apply for state permits for septics, but wondering how many you can install/build on a single property. 

(There is a price difference but suppliers have bridged that gap quite a bit due to popularity in the last ten years)Bathroom: Basic white subway tile to the ceiling for bathtubs/showers if surround is not desired.

During one of my rehabs they made me replace a brand new window I installed because it was 2 inches short from code.

I have currently installed dehumidifier and monitoring the status.