So in 10 months you would have paid for the machine, plus of course electricity monthly bill plus of course if you do manage to actually profit anything from botting because we know it's not easy and you might actually just lose $.
Renting one would enable you to test your 200 accounts method with only $100 plus of course the fact that you could expand to more servers at any time.
Also your server could get damaged and replacing any part of it would be extremely expensive.
Best of luck, I'm not hating just open to analyze the decision behind buying a server. I will discuss this further with you if you want.