Is this machine too much dough? Only you can answer that, honestly.
For some 5k is a healthy wad, others get nervous if the balance dips below 50k.
Now for practical biz advise...
Is this going to be sole income source? Have you ground stumps before? What's your maintenence abilities? What's your target customer?
For me, I started with a cheap, old vermeer 630, invested 3,500 and ground alot of stumps. It was small & old so I didn't take every stump I came across. I'm fortunate that I also have a tree biz that generates stumps. Just upgraded to a vermeer sc505 that I found used for About 1/10th new cost. 1,700 hrs...
Personally I'd be leary of dumping 50k at a machine that does just one thing without having an established market for it.