In the USA the big cities are fully paid, the suburban areas are a combination, and the rural areas are fully volunteer. I'm in a combination department, where the paid staff handle most of the medical calls and both respond to fire calls. The biggest issue with growing income inequality is folks just don't have as much free time to volunteer so it's hard to get enough members to fully staff an apparatus. That means paid staff but those are expensive and require a lot of logistics to maintain.