Have you done a break even analysis? Most research I've read states a minimum capacity of 7 barrels to hit break even. Smaller systems are more labor intensive and cost more to operate, requiring upgrades anyway on the way to profitability.
The guys in our area that are giving it a go were going to start with 1.5 bbl.
They eventually revised the plan to be 3 bbl.
Then they revised it again to 7 bbl.
Upon questioning them about this they said (paraphrased): You can't even break even at anything less than 7 bbl.
Those guys are planning on being distribution only because our state doesn't allow for a production brewery to sell beer at its facility - unless you're a brewpub all beer has to go through a distributor. Now, if you could sell half of your beer at retail prices out of your taproom, you could probably make a go at breaking even with a 3 bbl system.