Your best bang for the buck on used PCs are any of the Lenovo / HP / Dell small "business desktops". Typically known by their Tiny / Mini / Micro name (Tiny = Lenovo brand, Mini = HP, Micro = Dell).

For instance, the HP 800G5 goes for about $200 used and includes following:

• small 1l form factor
• i5-9500 (6c) CPU w/ VPro
• Supports up to 64GB DDR4
• 1 x 1Gbit Ethernet
• 1 x Wifi6 + BT
• 3 x USB 3.2 Gen 2 (10 Gbit)
• 3 x USB 3.2 Gen 1 (5 Gbit)
• 1 x USB 3.2 Gen2 Type C (10 Gbit)
• 1 x nvme slot + 1 x SATA SSD
• 1 x FlexIO port (small add-in card support for things like serial, vga, usb, etc)
• 2 x Display Port

Lenovo and Dell have similar models that are comparable. So find whatever is cheapest and most available.

All in all for $200 its more than capable for being a good little desktop