ECC is a ‘good to have’, but isn’t critical unless your systems are.

Most of the higher costs that come with stuff advertised as “server hardware” come from the need to get 99.99% uptime instead of 99.9%, because that 0.09% represents millions of dollars, or even people’s safety. If you just want to store personal data and run some basic services like a media server or a personal email, then pretty much any hardware will work, just make sure to backup your data regularly in case something goes wrong with your disks.