1)Homesteading and squatting are two totally different things. Homesteading is about getting back to the land, working to grow your own food and raise your own livestock. Provide your own heat through chopping firewood, get your own water by implementing wind/solar/other types of energy (or using natural flowing springs). Living a simple life.
Homesteading is about having a 'simpler' kind of lifestyle. (although it is a lot more work). You own your property, you own your home, you own everything.
Squatting is occupying property that does not belong to you; typically abandoned or vacant buildings.
2) You get a homestead like you get anything else... you have to work for it. You need to find a suitable home or piece of land, and buy it. Then you need to change your lifestyle to live back to basics.
3) Homesteading is as cheap or expensive as you make it. If you want to do something yourself, you may need to buy equipment/supplies. Or you can choose to continue paying someone else for certain items.
IE... firewood. If you have a supply of wood on your land, you can cut it yourself with a handsaw, or an axe... or you can buy a chainsaw. Then you can haul it out of the woods by hand, or using a team of horses, or with a tractor. Then you can cut/split it by hand (saw+axe), or with a chainsaw and logsplitter. All sorts of options that depend on how much $ you have available to invest in equipment.
4) Free... not to start. You have to own the land... which means you pay taxes on it. And you will need supplies, so you can't do it without some sort of income (money, trade for skills, etc)
5) No, you can't homestead on public land... this is considered squatting.
6) Yes... a homestead can be whatever size you make it. Huge log cabin, or a 10x10 building you share with the chickens.