Before buying an older Chromebook, look at when it reaches end of life for ChromeOS updates:
Samsung XE303 reached end of life a year ago, June 2018
If you’re looking to use a cheap chromebook after it’s no longer getting updates, and you’re technically inclined, check out GalliumOS, a Linux distro designed for chromebooks:
https://galliumos.org/
Or look in the specs where we stated this.