There are holes in the shingles at the peak of the roof that you can stick a finger through.

I cut a hole to identify the source and it looks like it was coming from the HVAC (currently set to heat). 

Welcome Matheus,Grab your favorite energy beverage, get comfortable, and get ready dive into the wonderful rabbit hole of Bigger Pockets.

While you do need it to refund any remaining balance on their security deposit, or an accounting of any deductions if you end up keeping the entire thing, the real reason you need it is because there could be monetary damages and additional rent they're liable for (since they're breaking the lease). 

The GOAL of this thread is for you to poke holes in my strategy and tell me WHY this couldn't work.

I also can't tell if Contractors B and C are just trying to sell as much work as possible, or if Contractor A really overlooked needed work.My best guess for approaching this is hiring a structural engineer to give me an assessment, on the assumption that they would not have a monetary incentive to try and upsell the work. 

I literally did everything from renting an excavator and digging the hole to craning panels in place, and the majority of the finishes.

Simply comparing cash flows without considering time value of money / timing of cash flows will be a large hole in your ability to weigh different deals.I look at both.

Second, anything that involves punching holes in stuff (like the walls or floor) should come next.

Long Term is better for you tax wise than short term capital gains.YOUR ATTITUDE: If you sell are you going to invest in something else (with a positive attitude), or go crawl in a hole and feel sorry for yourself.