They would be forced to hire illegals. They main part of immigration reform is to reform and expand the guest worker programs so there is no demand for illegals.
As for how much money an individual can make operating a leaf blower, that is limited. In my college days(60s) I worked as a groundskeeper one summer, but I also worked for a asphalt paving contractor, both being minimum wage jobs.
Back in the 1980s, I knew two brothers who began as teenagers mowing lawns and grew that into one of the largest lawn care companies in Dallas. They hired lots of illegals.
One of the problems with seasonal visas is that the season starts earlier and lasts longer in the southern tier of states so they are more likely to find H2B workers before the quota is reached, while those employers to the north have a much harder time.
Oyster processors in Louisiana can get H1B workers but those processors around the Chesapeake Bay cannot. A hotel in FL is more likely to get an H1B worker while the hotel in Maine will not.
The point is that we have plenty of excess labor in this country right now. They are undercut by illegals and temporary visa holders.
We do not need the extra labor. We need a smaller safety net and a competitive labor market that does not include indentured servants and illegal slaves.