Pinto beans are fab, too.
I buy them dried in Tesco.
Measure out what you need by hand, I usually do 2 cups and rinse them in cold water.
Throw them in a pan of boiling water with whatever you've got - a ham hock or bacon cuttings or no meat at all, whatever chopped veg you have (I always put in an onion and celery), plenty of salt and pepper, garlic, chiles, some dried cumin. You can even throw in a crumbled stock cube.
Simmer them with the lid on, checking the water levels every now and again.
They take a couple of hours and you can also chuck in a teaspoon of bicab of soda so the skin goes soft.
Then you can serve them in tortillas with rice as they are, with grated cheddar and soured cream and salsa.
Or, mash them up with a masher or two forks and fry them in oil or lard as leftovers, or lay them on a tortilla, cover with grated cheese and stick them under the grill till the cheese melts.
You can also use goat's cheese.
My father grew up on frijoles, rice and corn tortillas. Meat was for high holy days and then it was fajitas or cheap cuts and offal minced down and made into tamales or empanadas/pies or caldo or tripas (tripe) unless they had or someone had a chicken to kill, but chickens were very valuable for their eggs and were not killed off till they were old. Even roosters had worth till they were old.
Cheese was made from goat's milk, only rich people could keep cows. Even the classic Mexican sweet, dulce de leche is still sold in wrapped nuggets and made from goat's milk and cane sugar. The other is a nugget of quince seed jelly that you slice off by the piece.