Agree. If low cost and maximum value is you're goal, grab a used one of these or similar speed laptop (and you sort of get battery back up in that case)

Really, any machine from the last decade will be enough, so if you or someone you know have something lying around, go use that

The two main points to keep in mind are power draw (older things are usually going to be worse here) and storage expandability options (you may not need much storage for your use case though). Worse case you can plug in a USB external drive, but bare in mind that USB connection might be a little flaky