Gear is a pain in the neck. It gets in the way of diving.
It seems that whenever someone gets certified or thinks about getting certified, one of their biggest concerns is gear... They immediately want to buy everything in the shop. Perhaps this applies to you, perhaps it doesn't... I'm just saying that it seems to be a trend.
Be careful with this - it will quickly drain your wallet and keep you from having any left over money to actually do any diving.
Typically, too, by your 25th dive, you'll realize that what you bought isn't what you need or even want - your desires change quickly, sometimes many times, in your first hundred dives or so.
...Then there's the cleanup afterwards - the more gear you have, the more time you'll be doing the UNFUN part of diving - rinsing, drying, maintaining, replacing, transporting, and basically messing around with your life support systems.
That you are considering used is a great thing - most people new to the sport will immediately max out their credit cards at the dive shop - which frankly, is what's keeping most of the shops alive at the moment. Definitely make informed purchases, and like you're doing, consider used gear. You'll probably notice right off the bat that most scuba gear has a very poor resale value at just one or two years old, even if it's only been dived a few times. If you're the guy that buys new, then you're the one that took the depreciation hit... If you're the guy that buys used, then you get to take advantage of this fact.
There is a type of scuba gear that maintains it's value rather well - that stuff that your local dive shop (LDS) will consider "tech" gear - backplates and wings (instead of a BC), Jet fin style fins with spring heels (instead of soft, flexible, long, and sometimes split fins), solid, proven regulators like Apeks and Scubapro (instead of the stuff most shops sell that change annually) and marine-grade stainless bolt snaps (instead of a myriad of plastic or anodized clippy-doos). This stuff does not change from year to year, and it's ruggedness is unparalleled in the industry, so it's value is surprisingly high when it comes to resale. As any accountant will tell you, this means that this sort of gear is a better investment than blowing $5k on plastic "latest and greatest" that will be superceded within months. Scuba diving has been around for decades - it's very rare that a radical, new idea "revolutionizes" this industry, so beware of any product that promises to "revolutionize the way you dive" - that's code for "it was all BS anyway, and next year you're screwed because we'll 'revolutionize' it then, too."
Ask Tim (tgreene) about his recent experience diving with a group of newly-certified divers who all were sporting the "latest and greatest."
If you buy last year's "latest and greatest," then yeah, you should get a pretty good deal... Much better than buying TODAY'S "lastest and greatest." However, I suggest that you avoid the entire lame experience and purchase good gear that will last you for years and many dives... And won't be "uncool" in six months. Buy new or used - it doesn't really matter. What matters more is that you find exactly what you want... And that's going to take some diving for you to figure out.
Right off the bat, you're going to need a mask, fins and snorkel for your classes. Masks are all about fit - so you're going to have to check the dive shops by hand and find exactly the right mask. I suggest as low a profile as you can possibly have - if the glass touches your eyelashes, that's too low... Otherwise, the closer the glass to your face, the better. I also suggest a black-skirted mask, as the black doesn't yellow over time. Your basic one-window or two-window mask is appropriate - there should only be one or two pieces of glass in the mask. Other than that, it's all about fit - you'll know a perfect fit when you try it on - so try on every mask until you find it. Scubapros, Tusas, Atomics, Halcyons, Dive Rites, and Mares all seem to have their own followers, which is probably based on fit... So try them all out.
With the snorkel, stay simple and frankly, cheap - most divers never use theirs again after they get certified (you'll need it for class, but many never use it again). Even better is to borrow one from someone else for class.
Fins: With fins, there's lots of different schools of thought, but most of those that dive professionally, military divers, "tech" divers, and the like tend to gravitate towards Scubapro's Jet fin (or similar fins) because it's stiff and provides an uncanny amount of control underwater, which, despite what most of the magazines are saying, is what most divers value when it comes to fins... Not speed. Additionally, most divers will find that they can easily overkick ("fold up") soft, flexible, plastic fins if they really "lay into" the fin, which can limit speed... So many also find stiff, heavy Jet-style fins faster as well - which is very contrary to what the magazines say. Yes, it is true that soft, flexible, jointed and/or split fins are EASIER, but that comes at a price during the dive.
Thick, one-piece rubber fins like Jets also are heavy, meaning that they negate the need for ankle weights - something that was invented because the magazines kept telling everyone that lighter fins were better. All-rubber fins also have the advantage that one squirt of Armor-All (or food-grade Armor All sold in the dive shops as "silicone spray") makes them look brand new after a decade of use - that doesn't work with fins that have plastic on them.
Regardless of which fins you choose, spring heels are a favorite among seasoned divers because they won't rot or dry rot and break at the most inopportune time... And don't require any sort of buckle which promises to be "quick release," but in reality is almost never used and instead cracks or breaks - again, at the most inopportune time.
Anyway, that's my 2 psi on gear. Slow down. Look for the RIGHT gear, not just whether it's being sold new or used. Stick with the stuff that the seasoned divers are using (they've probably tried it all) - and I'm not talking about your instructor or DM, who's been doing this for two years - I'm talking about the diver that's been doing this for two decades and has at least 1500 dives to his/her name. And keep in mind that the longer you can get the dive shop to loan or rent you gear, the better... 'Cause when something breaks, it's not your problem - you just ask for another.
They say that the best kind of boat is your buddy's boat... Boat ownership is a pain in the neck, and it's much better to borrow than to own. With scuba gear, the same addage applies. Sure, you'll want your own gear eventually, and yes, it does get you diving more if you don't have to rent every time... But hold off on that and rent stuff for a while until you figure out what it is that you need and want before buying. Buying before you figure out what you need or want is putting the cart before the horse.
...And once you've decided what you need and want, THEN consider new or used.
