welcome to scubaboard ....
there is a terrific shop in illinois called diverightinscuba. if you want, give them a call and ask for mike. tell him i sent you (ron from jersey) and 9 out of 10 times he can give you deals so good that it doesnt pay to buy used.
not sure what your background is in scuba but if you dont have the ability to vip your own tanks and fill, it pays to buy new if it means only a few dollars more. for example, lets say someone here offered you an al40 for $70 used (or even $50). if you can vip, O2 clean and fill by yourself, thats a good deal. but if mike can get you into a new tank for $130 and the tank is already vipd and o2 cleaned???? meanwhile if you buy the used tank for $70 plus $18 hydro plus $15 vip plus $30 o2 cleaning for valve and tank, where did you save?
just my 2 cents ...
if you are all about used, i think i may have or know someone who can assist you somewhat more local. but as you can see, i am more interested in you doing what may be best as opposed to selling you gear....
either way, best wishes ...