I mean if you agree to it and they miss the first payment well then you know your answer. 

I’ve seen many investors miss oppportunities when combining primary residence use with investment strategies, but you seem to have timed this perfectly.

One thing I didn't see (or might have missed) was if you will be on site or if this is a remote situation. 

This wouldn't be mortgage fraud (because you are living in the property), and you are able to make some revenue from the tenants, or am I missing something here? 

They also noticed the furnace and hot water tank is missing / stolen. 

They missed the promised start date on the project by almost two months causing a cascading failure on dates since it was the roof, there were interior things, other dependencies that we couldn't do until the roof was finished. 

We are actually thinking about moving into the smaller unit. we are thinking if we should rent the main unit for long term rental or STR like airbnb but im afraid with airbnb, the non occupied days we may miss out on cash if its not rented out. 

Are there any other cons that I am missing for doing this?

When he missed his rent payment we gave him a notice to quit, he accused us of "entering his property without 24-hour notice", although I only knocked on his door and when he answered, handed him the notice. 

I'm also looking to get my hands on a good calculator for short term rentals since I'm terrible with Excel and only have a calculator for long term rentals that I know is missing sections that are specific to short term.Any help you can give me would be very much appreciated :) BiggerPockets has an Airbnb calculator, and I see that you're a pro member.Since you've read the STR book and done other education, you know HOW to pick a market lol.