It depends on how big you want to start off, how many breeds, type of breed and number of birds, type of set up, ect.

It would be easiest to start off small with one breed, one breeding coop (or free-range the birds in a secure area), one grow out pen, quarantine pen, incubator and brooder. Depending on how this is managed, it could be done very cheaply... Perhaps a $1,000 or so if much of it (coop, pens, brooder) is handmade or second hand and the breed is a productive, common breed that could be obtained locally. Selecting rare birds or multiple breeds will increase the needed space, number of pens, brooder & incubator capacity, costs of breeding flocks, ect.

Cost of feed, medications, feeders & waterers and incidentals is another consideration. The more self-sufficient and waste free the set up, the lower over all costs involved. The more biosecure the flock, the less risk of losses. Better quality and sourcing of the flock, less risks of losses. There are cheap, medicated feeds on the market that lower costs upfront... But feeding GMO-free, organic feeds and free-ranging can potentially increase your profits. NPIP & vaccinations is another consideration and will effect your consumer base.