Spray a small baking pan with cooking spray and add the sweet potato cubes. Spray the cubes lightly with cooking spray and roast in a pre-heated 375 degree oven for 15 - 20 minutes, until the cubes are lightly browned and tender. Set aside.
While the potatoes are cooking, cut the sausage in half lengthwise then slice into 1/2 inch half moons. Heat a large soup pot over medium high heat. Add the olive oil and swirl to cover the bottom of the pan.
Add the sausage moons and toss to coat. Cook for 7 minutes or so until the sausage begins to brown. Transfer to a plate using a slotted spoon leaving the drippings in the pan.
Add the onions to the pan and stir to coat with the drippings. Cook for 5 minutes until the onion begins to soften and brown.
Add the peppers and garlic to the pan and cook, stirring occasionally for another 5 minutes or so. The peppers should begin to soften and the garlic should be fragrant. Use a very small amount of the stock if things get too dry.
Return the sausage to the pan. Add the cumin and chili powder. Cook and stir for 2 - 3 minutes. Pour in the stock. Bring just to a boil. Reduce the heat to medium and simmer for 30 minutes or so.
Add the reserved sweet potato and the drained beans to the pot and cook over low heat another 10 minutes. Squeeze the juice of the lime into the soup. Stir and taste to adjust the seasonings.
Ladle into four soup bowls. Top with a few tortilla chips and some avocado cubes and serve.