I wholeheartedly endorse the buying of used gear. I have found most of what I have bought, mostly from eBay, yard sales, and the used room at several local dive stores is normally lightly used by divers who have either upgraded or given up on diving. Rarely will you find used items that are heavily used, because the owners want to keep on using it forever. When you do come across a piece of used kit that is worn out, it will usually be apparent, so you just don’t buy that.
In 18 years of diving, I have bought at least 20 used regulators, 6 or 7 harnesses and/or plates, 10 BC wings (spanning back and side mount), and 20 used tanks. I still have 90% of this gear, and use most of it at least occasionally. I have calculated that all this has only cost me about the same as 2 or 3 full sets of new gear and 4 new tanks.
Do be careful, though, in selecting the gear you want to use. Buying something the previous owner used once or twice is great unless he’s selling it because it’s not the right thing for the type of diving he wanted to do and will be the same for you. Whether you buy new or used, consider carefully, first if it’s the right style/model/size, etc. for what you need it to do. Otherwise, you may be the next person selling some barely used equipment for half what you paid for it.