It can get worse, if he was using subs as opposed to employees, and didn't pay them, they can lien you and stop any work as well until you pay up. 

If so that might change the answer about whether it is illegal since housing that is supplied to an employee ends when the job does.

There are also societal issues - historically, women had to be more concerned with reserving assets for the future in case the male died and she was left raising children on her own - and discrimination issues, wherein a lot of people assume the woman is in a secondary role (I see this in my own office with how some men interact with my female employees) - and early childhood issues - how many women are taught to "take risks" at an early age? 

I recently rented to employees of a construction company for a two month rental.

If I understand correctly, they do not have to be an employee or in any way compensated by you.

You cannot require that a GC get every DL (person info) of every trade/person who goes onsite; as GC's hire subcontractors and I assure you no legit subcontractor is going to send over their employees private information.

And, I got a chance to talk to one of the employees before they started.

I also had an employee call her who speaks Spanish. 

I see that I could go on HAR, Zillow, Redfin, etc and see what is currently listed for rent or already has rented, but I wanted to go deeper to see % of rentals vs sold(by neighborhood, zip, etc) and even demographic information as well.

Employees are always looking for accommodation.