He probably is running it all himself, it's only a 50 customer business. Combined with a day job that allows him to take the occasional personal call, it's very doable.

If you look on the DSLReports Wireless ISP forum, most of the smaller WISPs are doing exactly this, and eventually they may bring a person on to answer the phone, and an installer, but until you get a bit over 200 subs you can do this.