An M4 mini is an insane deal at $399 or $499.
A tip on storage, if you are ok with external storage, find a Western Digital D50 Thunderbolt 3 dock. You can find the version without an SSD pre installed for USD$100 or less, but the empty nvme slot is still there and will take any drive you want to slot in. Whatever you put in will not be as fast as a larger Apple or other built-in SSD, but will be just as fast or faster than the base 256GB Apple SSD. Biggest drawback is that you will not be able to use Apple Intelligence when booted to an external drive, but some may call that a feature.
A tip on storage, if you are ok with external storage, find a Western Digital D50 Thunderbolt 3 dock. You can find the version without an SSD pre installed for USD$100 or less, but the empty nvme slot is still there and will take any drive you want to slot in. Whatever you put in will not be as fast as a larger Apple or other built-in SSD, but will be just as fast or faster than the base 256GB Apple SSD. Biggest drawback is that you will not be able to use Apple Intelligence when booted to an external drive, but some may call that a feature.