i'd suggest finding local poultry swaps ahead of time, and stick around and see what sells and how much...
i just took 6 roos, 4 purebred silver grey dorking (culls) and 2 easter egger roos, sold all 6 before i even got the tarp off the truck for $5 each. found out everyone else was asking $15+. but then again, i went home with no birds, some took theirs back with em.
i take birds to the sales to get rid of em. usually the culls, mutts and oddball breeds. i'll take what i can get. usually $10 -15 for hens depending on breed, $5 for roos and between $5-10 for chicks depending on breed and age.
the sellers with chicks didn't do as well as those with half grown birds IMO. so grow them out 4-6 weeks, then take to a sale, charge a bit more to cover some feed, and watch the hens leave fast. so you get more for girls, a bit less for boys, but it all balances out.
last month in just 2 sales i made enough to cover 3 months of feed for my assorted cochin bantam and dorking flocks selling 9 roos, 7 hens and 4 chicks.
currently 23 adult birds, 12 about 6-8 weeks old, 16 under a week, and 40+ in the incubator due on sunday. oh and 24 month old quail and 7 adults.