Drain and rinse the beans in a colander and set aside.
In a large skillet, brown the meat over medium-high heat; drain well.
Return meat to pan. Add taco seasoning and 1-1/2 water. Stir to blend. Reduce heat to medium-low and cook until the sauce thickens.
In a large stockpot, combine taco-seasoned meat, onions, salsa, crushed tomatoes, beans and corn. Add water until the soup is the desired consistancy. (We have used as little as 3 cups for a more chili-like soup.)
Bring soup to a boil, reduce heat, and simmer for 30 minutes.
Top individual servings with a dollop of sour cream and a sprinkling of shredded cheddar.