Just ask for references in their application and require that one of them be a current work supervisor and call them.

I'm an active carpenter and have been in the field as lead carpenter and supervisor for the past 7 years.

I had to ask for a supervisor and went to the top.

In the 1970's and 1980's as robotics and computers worked their way into the work place, researchers predicted the demise of assembly and office workers.

you can serve them at their workplace.

I call their employers (direct supervisors) and try and ask open ended questions.

When a staff member did not know something they went to their supervisors and got back with me. 

Hello fellow investors,I'm planning to invest in Wichita Falls, and interested in areas with future development plans or new workplaces created,any advices?

It sounds like the son has given enough to verify his income but, I would double check verification of employment by simply just calling his supervisor from his work and telling them that you are a local landlord verifying an application for your rental.

The standard we accept in the workplace in today's world is staggeringly disappointing... so anyone who is worth a darn will always be able to find work.