Do I have to pay someone to sell a trademarked product?

If you put anothers trademark on your product and sell it expect to get sued shortly.

It depends. Is the source of the product the trademark owner? If so, you should be able to resell it. Are you saying you want to sell a product and use someone elses trademark on it? That is a bad idea. You can be sued for that. To determine whether you infringe or not, a court would consider factors such as the following: (1) strength of the plaintiff's mark; (2) similarity of the marks; (3) proximity of the products in the marketplace; (4) likelihood that the plaintiff will bridge the gap between the products (enter a market related to that in which the defendant sells its product); (5) evidence of actual confusion; (6) the defendant's bad faith; (7) quality of the defendant's product; and (8) sophistication of the relevant consumer group. If someone has received a non-final office action while trying to federally register a trademark, it just means that an application has been filed and is in process. It is still possible that the mark will eventually be registered federally. Keep in mind that state common law rights can arise just from using a trademark on a product, without a federal registration or any registration. There are a lot more questions that need to be answered before an answer can be given. One is whether the mark is famous. Another is whether the goods are similar or completely different.

Yes, typically you will have to obtain a license or a permission from the trademark owner in order to sell a product bearing the trademarked name. If you use the trademark without permission, you risk infringing the rights of the trademark owner which may subject you to liability for trademark infringement and damages. "Non-final action mailed" means that most likely that the trademark in question is not registered yet but is still in the process.