Welcome to SaleHoo!
Yes, ideally suppliers will allow you to do that especially dropshippers. You get to pick which products you want to dropship and list in your store. To clarify dropshipping works like this: You find a dropshipper and set up an account. Different dropshippers have different setups but usually you can choose to credit your account, or, you can simply leave it empty and pay for each item as you sell it. Once you've created an account, all you need to do is grab the dropshipper's provided photos and product descriptions for the items you wish to sell and list them on eBay or your website. After you make a sale and receive payment, log into your dropshipper account, select the product you have just sold and take it through the checkout and pay for it. Enter the buyer's shipping details, and the dropshipper will package it up and post it. Basically, the big advantage of dropshipping is that the dropshipper takes all the responsibility for handling and managing stock, saving you a heck of a lot of time!
Not all suppliers will require that you have an EIN or a resellers license or a sales t ax ID but having one would be to your benefit as it will give you access to more suppliers. Plus if you are intently serious about your online business, i t is best you get one, as you will be required by law to remit taxes for your income/sales.
Hope this helps :)