Brown ground beef in a skillet over medium heat until crumbly and no longer pink, about 8 minutes; stir in taco mix and water. Cook beef mixture until thickened, about 10 more minutes.
Place black beans into a saucepan and bring to a simmer over medium heat.
Spread 1/4 of the beef mixture on a serving plate and top with 1/4 of the black beans. Repeat with remaining ingredients to make 4 salads. Spread separate layers of romaine lettuce, salsa, tomatoes, and cheese over the salads. Generously garnish with sour cream and tortilla chips.