I currently work and make in the 70-80 range and just do landscaping as a side job for the "fun" of it.
The money is in the hardscaping definitely not the mowing. but its also hard work. I pulled down 15k this year just doing it on the side and only taking jobs i wanted.
Everyones market is different. here where i live you need to make 100k to be comfortable. the real estate is stupid expensive. i love my full time job and i love landscaping so i do both. the wife love the extra income and she frequently visits my job sites just to see the work i have done and has made friends with several of my customers.
My son is dating the daughter of one of my customers who spent over 10k last year on her lawn and plans to do more work in the spring and we go to each others family functions. I just am friendly and ALL my work is by word of mouth.