Redhawk is a fairly new name from Jayco. The Greyhawk name was around for much of the first decade of 21st century, either entry level or sandwiched between Escapade and premium Granite Ridge line. Before that, you will find Jayco's Eagle brand on C's. Jayco has also used the Melbourne name, formerly for their B+ on Ford chassis, more recently on a C on Sprinter chassis.
Jayco is historically a lower volume producer of C's than Thor's Fourwind division (selling Fourwinds, Chateau and Dutchmen brands), Fleetwood (Tioga and Jamboree), Coachmen (Freedom, Freelander, Leprechaun) or Forest River (Sunseeker and Forester), all of which supplied the rental industry with model lines positioned below the Greyhawk in price, trim and features. Jayco was in this market only briefly with the Escapade line.
Availability used will also depend on where you are looking. For a long time Jayco had less extensive dealer coverage, both regionally and in sheer number of dealers because of having exclusive territories. Thor got around this by offering three essentially identical brands so dealer territories could overlap. You will probably find more used Jaycos in the Great Lakes region than here in Oklahoma.
Tom Test
Itasca Spirit 29B