The owners of Reef Gliders - the Montgomery's - are also recent (2009) U.S. transplants - from my area actually.
Learn about Roatan diving with Reef Gliders Resort So they may be able to help.
Much of the inexpensive housing seems to be in the West End. Not necessarily along the main road where the smaller resorts are but behind it. Several of the shops have their DM houses in that area.
The advantage the West End has is that basically everything except the airport is walking distance. There's probably a dozen plus dive shops, lots of restaurants, bars, most of the nightlife is in that area. A couple of small food stores but more of that is in French Harbour.
http://www.roatanisland.net/grocery.htm
He definitely doesn't want to live in Coxen Hole - or even go there at night. Should he need it the chamber is at Anthony's Key - five minutes by cab from the West End. The doctor there also runs a clinic for locals and there's a doctor about 2 blocks from the main road into the West End. Another hostel while he's looking for something better is
Buena Onda
Some of the other AI dive resorts are more isolated - for example, Barefoot Divers is located on their own Cay. The dive operation also does some training but their DM candidates live in the West End and take a 20min. daily shuttle to work there. RJ mentioned Chillies above, the same people own Native Sons - a dive operation in the West End.
http://www.nativesonsroatan.com/index.html
It's sort of tourist focused but there's some good general area information here:
Roatán, West End
Have your son contact Gay at Coconut Tree Divers also. Their staff is from all over North America and she seemed to know everybody in the area.
Dive Crew | Scuba Diving | Roatan, Bay Islands, Honduras | PADI
Some friends stayed in a small apt. near the West End a few years ago while doing their DM/Instructor at CTD. I'm pretty sure it was around $500/mo. I've lost contact or I'd ask them where it was. It might've been:
http://www.magda-apartments.com/
Just for reference since IMO this place is too far removed from most things - here's an example of what $800/month buys.
Roatan, Bay Islands, Honduras Long Term Rental Home - Green House