Four acres is a lot without engine powered machines. I've followed a few market gardeners on youtube that use all the push/pull human powered tools and when they hit their mid 40s, they figure out they can't do it much longer or at least don't want to. It goes from a good work out to just hard work.
Kinda sad to see them when it happens. They have a look of fear and loathing and desperation. One guy is now mostly a podcaster. Another, Jean-Martin Fortier of Canada who wrote a book on market gardening now trials/hocks motorized equipment.
Market gardening is a game to get into when you are young. A few years back I looked at the road stand and said that we just did not have the time. So she took over. And has done quite well.
She has a major advantage in that we own the land that she uses and it was decent farm land to start but she has also worked very hard.