I don't know what the used sources are in your area. Probably CL and Kijiji, perhaps a local equivalent, e-bay, machinery dealers, networking, auctions, word of mouth, . . . . . It is tough to go very far for a used machine: you spend time and money getting there and it may not pan out.
What time frame are you working on? Do you have constraints on power, weight, transport, unloading, cost. If you can handle over 2000 pounds, 3 phase and any voltage, then some nice options may open up.
I bought my first machine used (close to new, very clean) from a dealer, I paid commercial shipping and had an electrician help me hook it up - it cost a lot. I learned a lot, I still have that first machine and use it quite a bit. As I gained experience, I kept looking for additional machines. I have since bought 5 more good sized machines, and several little ones, for about the price of that first machine.
Obviously, do the best you can, but it is a great hobby - jump in and get started. Nothing wrong with buying new. Actually, purchasing the machine is only the beginning.