My cousin owned one of the largest landscape companies on the east coast and I worked for him for several years when I was younger. He started in the early 80's with one truck, a trailer, a few mowers, and one commercial job. When he sold it a few years ago he had over 400 trucks and was servicing everything from Baltimore into North Carolina.
When the company was sold, he signed something saying he would not own or manage a landscaping company for X number of years, nor would he ever have any business dealings with past customers. A year or so after the sale, he started a new landscape company and went after all his old customers, and got many of them. He was sued by the company he had sold his prior business to and lost. I don't know what he had to payout, but it's had practically zero effect on him. He's still running and growing the same company he started, and he's as wealthy as he's ever been.
He got into banking shortly before selling his company and did well with it. As I understand he's worth north of $100 million. He started with nothing, and lived in an apartment when he bought that first truck and trailer.
I'm a big fan of the landscaping industry as a result of witnessing and taking part some in his successes. I will tell you this, he was a workaholic, and would show up before any employees, and leave after the last one. He also seemed to know more about his industry than any experts he ever hired.
Focus on commercial work. If after a few years, your brother isn't adding a truck or two to his inventory every year, he's not going to attain that kind of success from it.