If you're going to be spending $500-$600, look for used enterprise-grade laptops. Computers depreciate worse and faster than luxury cars. Enterprises (large companies) routinely lease hardware for 2-3 years, so there's usually a ton of it to be had. In general, enterprise hardware's designed for TCO (Total Cost of Ownership), so they're very reliable, easily field-repaired/upgraded and often there are complete service/shop manuals available for download on them that will show you how to do everything, step-by-step, right down to the last screw. There's also a ton of CHEAP spare parts available for them off Amazon/eBay. Cheap enough to keep on-hand. Extra genuine Lenovo power bricks - $10. You can't even get an Apple USB cable for that price.

I can't strongly enough recommend the Lenovo Thinkpad T (standard), X (ultra-light), P/W (Performance/Workstation) lines of laptops. My users absolutely beat the snot out of their computers, some in a literal sense, and they still run quite nicely. Almost half of the user desktops/laptops here are > 8 year old Lenovos, all upgraded to SSDs with max'd out RAM. I think we're going to cull the 10-12 year old ones this year, not because they're giving us trouble or aren't fast enough but rather before old-age problems like dried-up capacitors and dried-up heatsink paste become issues. We usually buy top of the line (new), max it out, run it forever. People end up becoming rather attached to "their" computer after having it for so long.

I do pick up used laptops for users' secondary (cross-border) computers, spares, etc. Similarly, all of our back-end runs on used enterprise gear. Switches, routers, IP phones, cell phones, servers. All used.

On the SSD vs HDD.. SSD is the right option almost every time. BUT, as with all storage, BACK UP OFTEN! The 3-2-1 rule of backups is a good one to live by. SSDs are more reliable than HDDs, hands-down. BUT HDDs give much more warning before they fail. Every SSD I've had fail died suddenly, without warning.