This will entirely depend on local market conditions and suchlike, of course.
One of my neighbours produces 10,000 litres of wine/year on ~4 acres of vines. An acquaintence runs a market garden on less than an acre. Another raises pigs in a barn on half that.
Take a trip through rural America sometime and look around. You'll see lots of very poor-looking households, but if you look carefully you might notice that they keep chickens and have a garden, and larger properties have more in the way of animals. Many are dirt poor, but they live off the land, and can afford to be dirt poor. Not romanticizing it or anything -- the homesteadies I know are not into being dirt poor, but they are into being more independent and living off the land so as to stretch their savings.
I'm not suggesting everyone can be Jean-Martin Fortier, but with sufficiently low overheads and access to somewhat affluent markets, it is possible to make a living on an acre.
This seems like an unnecessary distinction with no purpose other than to gatekeep. A bartender is still a bartender if they only work weekends. An artist is still an artist if it's not their dayjob. A barber is still a barber if they have to work another job to make ends meet.
No, you shouldn't delude yourself into thinking that farming an acre or two is going to replace the income of most 9 to 5 jobs, but at a time in history where we absolutely need to be working to preserve and promote small-scale farming, we shouldn't be gatekeeping people.
