Most cost effective solution for iOS development?

I'm going to be getting into iOS development at work, and I'd like to buy a Mac for my home so I can tinker with Xcode on my own time. I've never owned one.

I was thinking a late 2012 Mac Mini would be the most cost effective way to start, but honestly I'm not positive. Would an older version be fine too, or is 2012 even too dated now? Or is there a better machine?

My goal is to spend the least amount of money possible because it will be purely for iOS development. Any suggestions are greatly appreciated.