David Nebenzahl wrote:

Grinder, not sander. Yes, you can rent them. They come either in
hand-held or "walk-behind" versions. They take a little care in use in
order to get level results without divots and such.

Count on also renting or acquiring a respirator (not a dust mask).
Plus sealing off any nearby living areas you don't want coated with
fine concrete dust.

Hearing and eye protection too. And if you're a violin player forget the
whole thing, an hour with an angle grinder will leave your hands feeling
like they have permanent nerve damage.

Somebody suggested juse hiring a handyman who probably already has the right
tools. If it costs you fifty bucks to have someone do it you're probably
coming out ahead of renting or buying. At least that was the conclusion I
came to when I tried it. I did use the grinder again for a couple of other
things though, you can't have too many tools....