Heat the oil in a large skillet over medium-high heat. Add the meat and cook for 6-7 minutes, breaking it up into small pieces with a wooden spoon. Add 2/3 cup of water and the taco seasoning mix. Stir well to combine. Add the black beans and stir gently to combine. Cook until the beans are warmed through, about 3 minutes. Divide the lettuce among serving bowls. Top with grated cheese, the meat mixture, tomatoes, avocado, red onion, and cilantro. Squeeze a lime half all over each salad, then dollop with sour cream. Add some fresh jalapeño slices or a dash of hot sauce if you like. Serve with tortilla chips.