I have done this in the past, and will be doing it again, but it's for $25 a month, plus 10%. The last time I did it I got a lot of special orders, but didn't sell much off the shelves. The owner told me I had to pay him the 10% on the special orders and when I laughed he asked me to leave.
I'll be doing it again with another local place and the lady knows that special orders are not going to be charged.
It was good for me but that's no guarantee it will be good for you.
Good luck,
Bill