Depends on whether or not the .com is developed and for how long has it been developed. Their site will at least initially draw most of YOUR traffic. If the .com is for sale and you do not want to pay their price, then yes buy the .net and/or .org. We did that with my wife's business 12 years ago. Registered her .net and .org. In the next two years the .com just dropped and we grabbed it too.