You can always try craigslist. If you have just one child, yes maybe try renting. But if you have 2 or more, I think buying one (used or new) is fine as you have higher chance of someone actually spending time with the piano.

Lastly, I was told group piano lesson isn’t really worth it… You really need one on one attention with something like piano. I wish I had a chance to learn piano when I was young.