The ingredients were simple: warm water, a ridiculous amount of sugar (I think the recipe was a five-pound bag), one can of malt extract (Pabst was sold in local supermarket), one pkg brewer's yeast (also in supermarket). As I remember, the cost of the ingredients came out to like a nickel per quart.
Dissolve sugar in warm water, stir in malt extract (thick brown goo, thicker than molasses), add yeast. Cover and let it brew for a week at room temperature. There was a specification for hydrometer testing to determine optimum brew time, but I didn't have a hydrometer. Same kind of instrument that in those days was used for testing car battery acid.
What you got at the end of the week was five gallons of what looked like Ohio River water, cloudy yellow-brown with live yeast still in suspension, plus a thick sludge of dead yeast settled at the bottom.
Decant brew into quart bottles (I used surgical tubing for a siphon), add a bit of sugar to the bottle (less than a teaspoon) and cap it. I had a hand-cranked bottle capper that my grandmother used for wine from their Concord grape arbor.
The brew continues in the bottle. Yeast eats the sugar, gives off carbon dioxide and alcohol. Capped bottle forces the carbon dioxide into solution. You have to leave some space in the neck of the bottle to allow for CO2 to pressurize without breaking the bottle. Don't ask how I know that. Process goes on until all the yeast has died and settled to the bottom. If I were brewing today, I'd give it six months, but we drank it in those days after a week or two. Raw, but fizzy and definitely alcoholic. One or two glasses would get you stupid.
You'd have to pour the beer out of the bottle in one go, slowly and gently, to not stir up the dregs at the bottom. I think there is a clarifying agent that's used nowadays, or maybe something like a coffee filter. I didn't know about such things at the time.
The closest commercial product I ever found to what I made was El Presidente beer in Ciudad Trujillo, which was the state-owned brewery for the Dominican Republic. The bottle came with the authentic dregs at the bottom. Made me feel at home. Lots of pretty girls in Ciudad Trujillo. I miss them terribly. 'Restroom' was downstairs to the dark, dirt floor cellar, where you whizzed against the stone wall foundation. Unisex. Who needs civilization anyway!? The apocalypse will be fine. Fucking western civilization is a bunch of spoiled pansies.
If you google 'homebrewers association' they'll give you hundreds of much more complicated recipes.
Homebrew, far as I know, is legal as long as it's for family and guests in the home, not to be sold.