HansG

ok, here is the CURRENT answer -- please help other people by "upvoting it", since most other comments here are outdated https://support.squarespace.com/hc/en-us/articles/205809778-Creating-a-multilingual-site-in-Squarespace

the link no longer works!

$15 a month for a basic functional account -- also pricey, if you have limited needs.

if you do this advertising, please also explain why it's so incredibly expensive.

though you may also want to mention that Localize.js costs $49 (!) per month, even if you are using it as non-profit or for relatively small sites. This solution is most likely not relevant to many people who specifically want to build their own site, with Squarespae.