What you'll find is the margins are very slim in this arena. The expendables are relatively expensive and the price of the product has to be fairly low due to, as mentioned above, the flooded market.
For example, here in my local area there are 3 "larger" print shops. One of those shops got the contract with the local arena and they're the only one you see with substantial business. But, because of that, they can usually beat the other 2 shops prices for smaller scale stuff, i.e. the stuff like I get done. The prices there, because of their quantity, is almost at actual cost of the other 2 shops.
Now, where I have seen the other two shops more successful is at local events as vendors. At the track, at fairs, at events other than the civic center. Here they make stuff on site, within a few minutes of being ordered. Stuff like Cummins "C" logos (illegal actually, as its a copyrighted image), Browning logos, vehicle logos, etc....again, sketchy ground due to the copyrighting.
So, not to sound discouraging, but consider your investment in this area.