It would have to be a real piece of crap for the motor itself to not be balanced. But if you machine up some nice flanges for it, you can make nearly any old POS into a nice grinder. I'd recommend that the rear flange be on the order of 1/2" thick and very low clearance, or even a light shrink fit (0 clearance). Get an accurate rear flange and you're a good ways there in getting a smooth running grinder.
The reason I recommend going to that work is so you can buy 2 or 3 inexpensive 1/2 hp grinders and have assorted wheels set up and ready to go, without spending a small fortune. Successful grinding means making it handy to have the correct wheel mounted and ready to go, or else, you just won't do it, will ya?
Green 'morph' wheels are maybe good to relieve the steel shank from under a brazed carbide. I call 'em morph wheels because they change shape right in front of your eyes
So you need a grinder with a fine and a coarse AlO wheels to rough in drills and bits of HSS. Then a couple of CBN wheels to do the finer sharpening on HSS. And a couple of Diamond wheels to do carbide fine grinding. That's 6 wheels, so, 3 POS grinders
And that's just for off hand grinding.... tool and cutter grinders, drill sharpeners....those can be extras for when you graduate to needing one.
Edit: check Shars for diamond and cbn wheel kits that won't break the bank. Some of their wheels are not accurately made.....I dunno why anyone would go to the trouble of making something that looks exactly like a diamond grinding wheel but couldn't be bothered to center the aluminum blank under the ring of abrasive. For me, it's cost prohibitive to return it, but you could and should until you get good running wheels, on your accurized grinder.