I need to get the initial edge on new chisels (the "hollow grind").
Everything I've read says to use a slow speed grinder with aluminum
oxide wheels to prevent overheating of the steel (which ruins the
chisel).

I've been told that the grinder should not exceed about 1200 RPM. One
local woodworker actually keeps a cup of water next to his slow speed
super expensive Baldor grinder. He grinds for about 5 seconds, dips the
chisel in the water to cool it, and repeats the process.

I currently have an $70 Delta 1750 RPM grinder. I can get aluminum
oxide wheels for it, too. How risky is it to use it?

I'll have the cup of water to prevent overheating.....