There is a demand but you have to find the audience. Most Property Managers don't understand how to use a remote service and/or are reluctant to give it a try. If I ever lose one of my current managers, I would consider replacing them with a virtual assistant (or two).
I would tell him to look at joining the NARPM group, I think that he would find that this is a great way to break into this PM group. If he is serous about doing this full time on a professional level,, he should make sure that he is licensed and insured, and can handle the workload