You can get ripped off by purchasing from a disreputable store which doesn't stand behind its merchandise. You can get ripped off by purchasing through the mail and not receiving what you bought, or by getting a sub-standard product. You can get ripped off by purchasing a used telescope that is a piece of junk the owner just wanted to unload on an unsuspecting person. In short, you could get ripped off. Don't let this prevent you from buying a telescope.
Consumer fraud is present in every sort of industry, after all.
Think before you buy. Please don't let a hasty decision cause you grief and prevent you from getting into this cool and exciting hobby. The advantages of this method is that you have someplace to return the telescope to if you have problems with it. Some places even offer your money back if you change your mind within some grace period. The disadvantage is that you generally pay more for the telescope itself, and you pay sales tax.