The same analysis could be made between selling and investing in a non-1031 compliant vehicle.   

The owner of the vehicle contacted me initially asking for money to repair the car.

For this market and alternative investment vehicles, I would consider these properties to be solid investments.  

My tenant (tenant 2) in another unit just contacted me stating the tenants responsible for shoveling damaged her car while shoveling the driveway (tenant 1 apparently used the car as leverage to pick up the snow and scratched the other tenant's car in multiple places all down one side of the vehicle).

You can track expenses and upload receipts, organize your progress pics, documents, vendors, leases, vehicle mileage logs, and some other things.

He was thinking of selling it for 90k, pay off two vehicles and take 60k to put down on a new house to live in.

I never thought about making real estate the vehicle for my financial freedom until now.P.S. 

Additionally, they reinvest cash from the equity in their rentals into other rentals / vehicles in order to maximize their return and prevent "dead equity" from "diminishing" their ROI.  

Are these vehicles looked at the same way as your standard rental car, or do they have unique, accommodation-type requirements to fulfill?

I have used most of my cash to get it up for remodel and carried some on cc, and refinanced an inexpensive paid off vehicle to complete the job.