During my senior year in HS I managed 45 lawns per week on Friday evenings and all day Saturday. I NEVER worked during the week. The only way I was able to expand each year was to keep buying more equipment and hiring more helpers because the rest of my week was spent on homework since I was taking 4 AP classes at a time.
My parents kept telling me I didn't need so many mowers to do my job, and I know that anyone else who worked all week could do 45 lawns with 1 or 2 mowers, but I made tons of money and have no regrets about tailoring my expansion to my limited time slot. I'm just glad they didn't try harder to hold me back because I have never been happier in my life than when I was mowing.
My advice: Set aside a time that will always be reserved for lawns that will not interfere with school or golf so your customers get some consistency, then get as many accounts as you possibly can, then buy as much equipment and hire as many helpers as you need to get them all done.
Remember, if you get more than you can handle, you can always SELL the accounts, and if you include your equipment with the accounts, you can recover all of your investment there too.
Lesco 48" hydro for my own yard
Used to have:
Ferris 61" DD walk-behind
Lesco 48" hydro 17HP Kawasaki
Goodall 36" belt-drive
And some change
Not mowing commercially since 2000