Last year I bought a second hand Lenovo Thinkpad T510 for $20.00. It had a 320GB hard drive, 4GB of RAM and Windows Vista Home Premium installed. It was clearly struggling to run Vista.
I upgraded the RAM to 8GB, and swapped the 320GB HDD for the KingDian SSD. I then replaced the CD/DVD drive with a hard drive caddy and installed a 1TB HDD. The CD/DVD drive is now optionally connected externally via a SATA to USB cable.
I then installed Linux Mint 18.3 (64 bit). With its i7 processor, this beast really flies. It is as fast as any current business laptop for a fraction of the price.