What's your area climate-wise? Some breeds don't do well in heat, some breeds don't do well in cold...
What's your local demand? Is it all rural communities with backyard mixed-breeds, or is it schmancy uptown backyard henhouses with several hundred dollars invested in three hens? Is there a 4-H market?
Where would you be selling/to whom would you be trying to market?
Ebay, the local auction barn, craigslist,
Tsc swaps?
What would you be selling (eggs, meat, chicks, hatching eggs?)
How large an initial investment are you willing to make?
Do you want eggs/meat for yourself? Bantams wouldn't be good, if that's a hope.
What appearance do you prefer in a chicken?