I went from a 1 TB M1 Mac mini to a 512 GB M4 Mac mini. I still have 335 GB free. I keep my big Photos Library on an external USB 4 / Thunderbolt SSD.From reply 447 above:
"Having a limited budget and wanting the best value I have naturally wanted to buy the base model but I am not at all keen on the very restrictive storage of it."
If you buy only "the base model", you may find yourself unhappy with it before too long.
I'd suggest the m4 Mini, 32gb of RAM, and a 1tb SSD.
That should remain competitive for 5-7 years ahead -- it has "room to grow" that will fit the growing demands of the OS.
To save money, IF you have the ability to buy from Apple's online refurbished page, get it from there.
You could get away with 32gb/512gb, with an external SSD.
But you want to be able to BOOT and RUN from the internal SSD.
I found 1 TB was either too little or too big. With the Photos Library on it, it was way too cramped. With the Photos Library moved to an external drive, the 1 TB internal SSD was huge overkill. 512 GB internal SSD with an additional external SSD is by far the best solution in my situation.