No, not the ones I've worked with. They should just be happy you're attempting to get sell their merchandise for them.
If you find a company that charges monthly fees if you don't sell a certain amount of their products, run as fast as you can....in the other direction! Most drop shippers charge no fees whatsoever, and a few charge a minimal fee....usually $1.00-$5.00 per shipment....the latter being just an extra monay-maker for them. (I wouldn't recommend these either.) Jim
There shouldnt be a fee... the only time I can see it being applicable is if you have negotiated a lower rate on the promise of selling X units however most will not do this and at best have a sliding scale which automatically adjusts what you are charged based on a rolling 12 months of sales