A variation of this is to charge nothing for the listing but a high fee paid in advance for the resulting publication which may or may not be published. Also beware of groups offering to print your poetry or short stories in anthologies and for which you must pay in advance to reserve your copy. If you are offered diamonds or precious stones by mail or phone, you are more likely to get cheap gemstones that have little or no resale value. Reputable diamond dealers may advertise, but they seldom, if ever, sell valuable stones by mail. Don't buy if the dealer won't allow you to get an appraisal first.
Gold requires careful assaying.
Buy gold only from legitimate dealers and only if you are really knowledgeable about gold investments. There are also phony land and oil lease investment schemes that promise you great wealth very quickly. Always check out investment opportunities thoroughly. Always avoid such pressures. It is extremely doubtful that your house will start tumbling down around your ears that very day.