He's no longer in control, and wither he wants to complete the short for his own interests, or he doesn't. 

I design and build our own projects therefore we have a better control of design, budget, schedule and labor.

This is where I get lost.

The monthly lease was $3,500 and this translates into $35,000 in lost revenue.

An investor that owned 100 rental houses say in the Bay Area would be controlling well over 50 million dollars worth of RE in our market it would be 20 to 30 million.... in the mid west rust belt is could be 2 to 5 million..

What questions should I ask the seller to prove that he has the controlling interest of the property and has the right to sell?

The key is understanding how it works in terms of it's structure...Corporation -> Workspaces -> Apps -> Items -> FieldsI will say that while Podio itself is great, you really need to integrate GlobiFlow so you can create automations to help control the flow of your data and create tasks to run your business on.  

I've been driving for dollars lately, and have already found some abandoned homes in my area, yet I am at a lost of what step to take next. 

I estimate $15,000 - $20,000 in repairs and lost rent.

To start, I am 28 and completely lost right now.