When you're selling wholesale, you'll likely want to have a minimum order requirement. This is done, in part, to ensure that the buyer truly has a business where they will be reselling the items, rather than just purchasing for their own use (or perhaps themselves + their friends). It happens, trust me!
You can set your minimum however and as high as you'd like. Generally if the minimum is $100, that means the buyer can order items worth $10, $20, $30, and $40 (or whatever $ values add up to at least $100). You could require a minimum of 6 prints of whatever design they order. Minimum requirements per item can be combined with a total minimum order requirement (minimum 6 per style and $100 minimum order requirement).
One important thing to remember is that if wholesale customers see your retail prices, they will likely want to pay you 50% of your retail price. So be sure your retail prices are high enough to leave you with a decent income. Some artists prefer creating an entirely separate line for wholesale, one that they don't offer at retail. And sometimes there are things that just can't be sold at wholesale because it's unlikely they would sell if the wholesale buyer priced them at 2x cost.
