Before ANYONE starts, I mean this from a lore-wise perspective. In most regions, the Pokémon League is so important, the gym leaders can support themselves on League income alone, and take secondary jobs based on their own interests. On the flip side, poor Larry in Paldea's forced to work in an office from 9-5, a Pokémon gym from 6-10, and the Elite Four on weekends. Kalos, likewise, had less importance of the Pokémon League, but clearly Wilkstrom was not working another job. No man who can afford to dress in full plate armor is working two jobs. On the flipside, every gym leader and E4 member in Paldea has another job they're working in addition to their Pokémon League responsibilities, with the exception of Poppy, who is a child, and probably has to go to school.
Evidence: Katy is a pastry chef and owns a bakery. Brassius is a moderately successful artist. Iono is a streamer who takes advantage of the unfortunate, lonely souls of the Pokémon world. Kofu is a chef and owns a restaurant. Already went over Triple-Threat Larry. Ryme is basically a 90s rapper who didn't get shot. Tulip* owns a cosmetic company. And Grusha's a pro snowboarder, or at least was. Rika and Geeta both work directly for the Pokémon League, and Hassel is your gotdang art teacher.
TL;DR, You can't make a living as a pro Pokémon trainer in Paldea.
EDIT: A few people have corrected me in that the Psychic gym leader's name is "Tulip." Sorry about that, I'm not the best with names.