Hi Kevin i do gardening for a living. I been doing it full time from the day i left school 8 years ago now ( i getting old now ) I work for my Dad who been doing self employed for the last 35 years, so can make a living out of it but i wouldnt expect to be a millionaire or well off. They is a lot of hardwork involved in gardening as alot people know doing there own garden.
Like some other people have said what side of Gardening are you interested in? There is landscaping/designing - garden maintenance - tree surgery etc. I do garden maintenance and the odd bits of tree surgery. Most of the money we make is in Grass cutting, we do over 150 gardens for grass cutting some have it done fortnightly or once a month, we normally do hedge pruning now for privets - bux etc but most after the grass has finished growing.
I personally like the plant side, i like grow thing so i grow a few extra bedding plants for anyone who wants them. And i would like to do some garden design.
A lots of your costumers you get to know really well, its really nice when they make a brew and you can have a good chat
One thing you must consider is cost of machines, they cost an arm and a leg New. A decent second hand lawn mower will cost a few hundred pound. And maintaining the machines - cost of fuel - van/trailer - tools etc.
There not a lot or hardly anything to do in winter
If you like any more info or any questions just message me and i get back to you.