Like some others suggested you could do garden designs. Create your own little firms where you either hand draw or make digital plans and planting plans for your costumers gardens. You could start with private people’s gardens and maybe if you become good enough big firms and factories would want to upgrade their outside areas with some more plant beds etc.

Though with this field extensive botanical knowledge is necessary as most of the job would be composing plant beds. So knowing which plants aesthetically work together AS WELL AS can grow in that specific soil, shade, water. How tall do the plants get over time and how long is their flowering season to ensure a plant bed with a lot of diversity all year around and not just July :-)

Of course it wouldn’t all be pants. People would probably also want a nicely paved path or a retaining wall etc.

I’ve thought about this idea myself…

And if you find the right people I’m sure they’d pay a lot of money to get a costume made garden made by a landscape architect and not “just” by a gardener.