It's being done, but it's really robbing out some areas
I think I'd find the suppliers, and ask if they need more pickers. Otherwise you'd be competing for markets that you don't have any in depth information on, or access t,o at present.
If nothing else what they supply will give you an idea of what's likely to sell.
There's another point though, legally you can't pick for commercial gain without the express permission of the landowner(s) and if you do, and you are found out, it's theft. (Please mind that the forum won't allow the promotion or encouragement of illegal activity) I don't know the penalties for picking without permission, though I doubt it's like the water bailiffs and the confiscation of equipment and transport as well as whatever the Sheriff throws at you.
Why the interest ? are you taking a notion to it ?
cheers,
M