MartinF Heya Martin,
I did a quick google and they'd be around 1500-2500 depending on condition and how quickly you wanted to sell. Bearing in mind a new C40 (the current entry level yamaha) is around R2500+ a.t.m so there's value there for the buyer.
Actually a good time to sell these as it's back to school and some kids will need student guitars and these would be perfect.
SAMIS (South African Music Instrument Store) group on facebook is a good place to start advertising, Gumtree isn't bad either - just be aware scammers are active. Other options are Cash Crusaders or selling/consignment at the Gear Junkie.