Have you tried contacting a local community bank? 

One was taken over by some squatters causing problems for the neighbors and the police were contacted who contacted the lender.

And each year when the lease comes up for renewal, I ask them to contact the housing authority and ask for a rent increase.

Can anyone recommend sources for contact information for property owners?

If you're not sure of you preferred direction with your next property I would invest in understanding investing more thoroughly and read 5-10 books as well as speak to other experienced investors.

And I'm sure that's because some people direct book, others use Airbnb, etc.

Always have a clear exit strategy, whether you plan to rent, flip, or sell the property down the line.If you or your son are looking for more hands-on guidance, feel free to reach out directly.

Marc Mosseau was the leader at this Oklahoma City funding tour I went to and said contact me with my first deal.

Leveraging our market connections, we identified the property’s potential and negotiated favorable terms directly with the seller, securing it at a highly competitive price.

And IMHO, the prices are dropping big time (on avg. 10K/month...houses that were above 300K a year ago are not selling at 250K now) and the available rentals saturation is worse than I seen during summer season (with rents dropping from 1$-1.08/sqft to 0.8$/sqft and very little contacts and applications...just go in Zillow and look how many rentals are on the market now in Kyle, New Braunfels or Converse).