There is some much to the hobby you will need more than a detector.
If you buy used, buy off someone you know. As for used, well no warranty. Detectors are pretty tough even though they use light materials like plastic to make them. I started with a very easy Bounty Hunter and I dug a lot of trash. It was deep enough, but most finds are within 3 inches of the surface. If you are going for 12 inches your going to need a good relic machine with good discrimination. Hunting by visual readouts produces poor results at best for your deeper targets. My experience has shown me after 5 inches most machines loose the ability to ID a target. There is things that will fool any detector, and there is a science behind that. I will take a chance and say most of us hunt mostly by sound. You dig and move on and dig again as quickly as you can. When you have dug 100 pull tabs you get tired real quick. But some machines do a better job telling you what you are digging. You could just discriminate the pull tabs out, but gold rings fall into that area. You gonna do your yard or the city park, well you will soon realize how are these guys posting these great finds. I wish I was there, I could let you use my different machines so you could get a real feel for what I am saying. If you cant wait, buy anything. Dont expect great results at first. But even a veteran detctorist like me can find stuff with any detector. Save your pennys and upgrade if you plan to stick with it. You will never get rich. I started looking for meteorites and now I prospect, relic hunt, coin shoot and as much hunting as I can find. I think the tesoro will do you right. But any detector will work. Good Luck.