you could expect to profit from the sale of unwanted domain names are sadly over. Most meaningful dotcom have been snapped up, and unless you have something really outstanding I wouldn't bother too much.
Way back in those heady dotcom boom days I was approached out of the blue by a big american software company which wanted to buy a name that I had registered. A lively week of negotiation ensued. They ended up with the domain name and I ended up with a slab of their dollars. I still dine out on the memory.