If you choose this option, make sure the buyer knows up front so that he can make the necessary arrangements. One thing to remember is that UPS, at least will send whatever is Collected on Delivery to the shipper's address as recorded in their files, and NOT to the return address on the package. Respond to an advertisement in a prompt manner. You might be pleasantly surprised. State clearly your terms and intentions and follow through on them.
Nothing angers a seller more than delays and excuses.
As radio equipment is generally bulky and fragile, allow for a reasonable amount of money to package, insure, and ship your purchase properly. He or she will be more than happy to either ease your concerns or confirm your suspicions. It's generally a good idea to include your geographic location and a phone number where you can be reached somewhere in your posting as well. Besides reassuring your potential buyer or seller that you are a real person, it's often easier to bargain and make other arrangements on the telephone than through a protracted electronic mail exchange. Some buyers prefer dealing with folks in their local area, too, as that makes it easier for them to inspect the equipment before paying money.