Mushroom compost is widely available, and I can get five cubic meters of that delivered in a truck to my driveway. That has fertility but some pH problems.
That is very interesting to me. I tried mushroom compost here...Once.
My delivered product included used condoms, medical supplies, and other unspeakables...that was only what was visible to my eye.
Honestly, I was shocked. I swore never again.
I bring nothing in... absolutely nothing. I have a closed system to the extent possible. I raise cattle, they provide income and more importantly to me superior organic matter that I compost. I raise legumes like Sunn Hemp which when combined with catle manure and composted produces the finest garden soil amendment I have ever experienced. I raise fish in ponds. In addition to food, they also provide extremely high content garden amendments. I capture rainwater...etc, etc. I do purchase some seed externally but mostly rely on my own internally. That is just the way I roll.
