In a medium saucepan, bring 2 cups of water to a boil. Add the rice, reduce heat to low, cover, and simmer for 15 minutes or until rice is tender and water is absorbed. Remove from heat and let it sit covered for 5 minutes.
While the rice cooks, heat olive oil in a large skillet over medium-high heat. Add the ground beef and cook, breaking it apart with a spatula, until browned and cooked through, about 6-8 minutes.
Drain excess fat from the skillet if necessary. Stir in the taco seasoning mix and 2/3 cup water. Simmer for 5 minutes, stirring occasionally, until the sauce thickens and coats the beef.
Add the black beans and corn to the skillet with the beef. Stir to combine and heat through for 2-3 minutes. Season with salt and pepper to taste.
In a small bowl, mix the sour cream with lime juice until smooth to make the lime crema.
Fluff the cooked rice with a fork and divide it evenly among four serving bowls.
Top each bowl of rice with the seasoned beef mixture, shredded cheddar cheese, diced tomato, red onion, cilantro, and avocado slices.
Drizzle each bowl with the lime crema.
Serve immediately and enjoy your ground beef taco rice bowls.