The last park only pulled criminal record.

Do you have a screened criminal report on him..  

Now if the 2nd applicant had a criminal history and recent big time credit issues, taking them on may be a question, but from the info provided I would proceed with them. 

If they decide you're acting as an agent without a license:1st offense - $500 fine2nd offense - felony 

If so that is criminal behavior.

The other 3 all make my 3.5x gross no criminal no evictions decent credit (620-650 for tenants).

I think part of the offense they took may also have been from the fact that they had invested a fair bit of time in working with me, and I had then turned around and not hired them after seeming to be very interested (which I genuinely was -- but I also wanted to make sure I was getting the very best balance between price and quality that I could).I don't have a lot of experience dealing with contractors, so I'm honestly wondering if I committed a big faux pas, or if Company B is just unprofessional.

If, however, you think that you might stay in your current career, I would focus on enhancing your current earning capability - sounds like that would be a JD, Criminal Justice, etc.

No offense to your mother, but if she had been raising the rent every year over the last 20 years, she'd be sitting on a few million instead of pondering her retirement plan. 

First job on any renovation job site should be wiring and installing a security system with video and remote monitoring and make it prominent and visible to dissuade lazy criminals.