I think it depends on your definition of "living off the land". Walking off into the woods and starting with just what you can carry is nearly impossible. Raising and growing everything you need to sustain yourself on your own land is more doable.

I can raise enough meat to feed a family of 4 through a year as well as enough milk to keep the family going and enough vegetables between gardening and gathering to sustain a family of 4 on about 5 acres of land. A dozen or so hens and a rooster will produce enough eggs for the family and to hatch the occasional batch of chicks.

With the occasional walk about to gather wild greens and berries during harvest times.

The problem comes in in the form of staying on top of all the work. You will have to all work together all day to keep up.

Storing food becomes much more important and waste is your enemy. Also, knowing what to gather is really important. Everyone mentions cat tails to eat but realistically how many cat tails are you going to find in a year? Not very many.

Yet, Polk salat grows everywhere in the spring. With a little work enough can be gathered and canned to store away 50 quarts of greens for winter. But you have to know what it looks like and how to prepare it. If you boil down Polk salat and eat it you will pay for it with severe stomach cramps, diarrhea, possibly to the point of death. But if you boil it down, drain it (water will be green) put in fresh water and boil again. Repeating until the water is clear at the end of the boil (usually changing water 2 or 3 times) it tastes like collard greens and is excellent cooked in with scrambled eggs.

Knowing when the dew berries and black berries will come ripe and where they grow is important. Knowing when muscadines come ripe and where to find them. Remembering to take a rifle with you while gathering muscadines is important too. Black bear real like muscadines.

You will have to become less squeamish about what you are willing to eat. If you kill a chicken hawk that was after your chickens, you eat the hawk. If you have a trap line going and you catch a bobcat or a possum, you eat them.

Being dependent on the availability of big game for meat is a bad idea. They are not always around when you want to kill them. So when they are around you need to take advantage of it. Then you need to know how to preserve the meat before it spoils.

You are much better off raising rabbits. Rabbits produce more meat in a year then cattle will. (Especially factoring in how much they eat). And you don't have 1000 pounds of meat the get put up all at once.

This is how my wife and I live now. We still buy stuff from the grocery store while we can and put back supplies for a bad growing season and stuff we can't produce on our own (such as salt and some grains) but the majority of what we eat comes off of our land.