If you want to learn how to use a CNC, and, as you say, get your feet wet, then that Bobs CNC E3 might be OK.
But it's not even remotely close to being anywhere near a $4000 machine. (I'm just basing this on the picture on their website - I'd never heard of them before)
You can probably sell it when you're ready to move on, and get at least $300 back, if it's still in good condition.