I always like to think about what the revenue model is. Either you get paid by the customer (flat fee or a percentage), ....or essentially you become the specialty retailer that locates specialty items, buts them at wholesale and sells them to your customer at retail. I`d have to think through whether or not the retail model could really work since you wouldn`t be buying in volume, but say you had to buy in lots of 10, the customer seeking the specialty item could prompt your purchase of the "lot", sell one to your customer, and post the others for sale in your online store. In this approach, you would need to be, and could be, selective in the lots of items you`d buy because you don`t want to get stuck with inventory, but if you believed the item to be one that others might desire, this could work.
The model of buying an item and charging your customer seems simpler but there are issues with this too. How much do you charge? (how much is the customer willing to pay?) For example, for OHDenise`s underwear, the value of your time (and the amount you`d have to charge) could be more than the cost of the underwear, thus making it a difficult model to execute. (by the way, my comments about the cost of OHDenise`s underwear are strictly hypothetical of course)
This could be an interesting opportunity. Let`s keep thinking....