My advice is... Pay once, cry once! In my experience, if you buy a "cheap" motor, you might as well buy 3-4 of them at the same time, because it's not a matter of IF they will fail, its WHEN.
For a grinder application you're gona want a TEFC (Totally enclosed fan cooled)....the motor in the link you posted appears to be a "open" motor (has the cooling cutouts in the housing)..... steel dust will get in there, and burn the motor out quickly in a grinder application.
I'd recommend looking at these folks:
http://www.electricmotorwholesale.com/LEESON-116594/
That link is to the motors I use on my grinders..... but if you look around, then have the best prices on just about any size/brand of quality motors.