It might be a challenge to find many used 7D2s.... though I'm sure they exist. It's a pretty new model. If you can wait a few months, you'll start to see them show up at Canon's site for sale as refurbished cameras. Canon Refurbs now carry the same 1 year warranty that their new cameras do.
I have a 60D, 70D and the 7D2. I plan on selling the 60D when I get around to it. The 70D is a very fine camera. I'll most likely keep mine for macro and a few other things where a tilt screen comes in handy.
That said, for lightning quick AF and frame rate, the 7D2 shines. I'm getting bird photographs that alluded me before. Is it expensive? Yes.... twice what the 70D costs. Is it worth it? Only you can decide, based on what you shoot. It has been worth it to me. I'm having a blast using it.
Kim (the male variety) Canon 1DX2 | 1D IV | 16-35 f/4 IS | 24-105 f/4 IS | 100L IS macro | 70-200mm f/2.8L IS II | 100-400Lii | 50 f/1.8 STM | Canon 1.4X III
RRS tripod and monopod | 580EXII | Cinch 1 & Loop 3 Special Edition | Editing Encouraged