@Jill558
If I wanted someone to manage my property I would join the local host group and ask for recommendations there for experienced superhosts who also co-host. Rather than employing a management company, who will be more expensive and don't always offer the personal touch.
Using a local superhost also has the advantage that you can check out their reviews.
Taking up references and having a contract with any co-host/property manager goes without saying.
As mentioned above, your client needs to check local regulations around the legality of using his investment as an STR.