>>1926825You need a battery that costs at least as much as the engine.
You will need to fiddle with a LOT of things while assembling it (chain line, battery brackets, cable management, etcc...).
Overall, for under 1k, you are probably better off buying a cheap ebike.
I'm very happy with my choice though. But that's just because i got the time, the tools, and the free frame and wheels.