We bought our son a 5D (now C) not long after it first came out. It motivated him to get a job as a photography assistant in the greater NYC area. He learned a lot and some of the photographs he took with that camera are printed and hanging on our walls. It was a great camera, at the time.
So.. a few months ago, I picked one up for $300 with a lot of extras (batteries, charger etc.) I was able to find a used RRS L bracket for cheap as well.
Is it better than the 70D I "loaned" to my wife? I don't know. I do know, I've used it for a few photographs of my wife and they came out very nice. It has its limitations of course, ISO being one of them and it's only 12 megapixels, but in the right light, with the right genre.... a good lens, it's pretty cool.
I just put my 16-35 on it... and compared the FOV to using it on the 1D IV.... takes a few minutes to adjust. It's the widest lens I've ever had in my hands... sort of cool to be able get the lawn in the foreground and the tops of 100' tall pines at the top.
Anyway, we all know the 6D has fewer limitations and is an amazing camera at today's prices. I bought my 5Dc back before the 6D Mark ll came out so the prices for used 6D's were still up there pretty high. Team Speed is probably right... save a bit more and pick up a gently used 6D. From what I've read, you can almost shoot in the dark. 
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