Bring a large stock pot of salted water to a boil.
When water is boiling, add corn and boil until tender, 5 to 7 minutes.
While corn boils, heat a nonstick pan with some cooking oil over medium heat. Add beans and saute until fragrant and warmed through, 1 to 2 minutes. Transfer beans to a mixing bowl. Wipe out pan and return to medium heat.
Combine beans, cilantro, and cheese.
Return to heated pan. Place a tortilla in the pan, top it with bean / cheese mixture and then another tortilla.
When the tortilla on the bottom is golden brown and crisp, flip the quesadilla and cook on the other side until all of the cheese is melted. Continue with the remaining tortillas and filling.
Scoop out avocado and mash with first part of lime juice. Season with some salt and pepper.
Brush corn with butter and second part of lime juice. Sprinkle chili powder over top.
Slice quesadillas into wedges. Serve with sour cream and mashed avocado. Enjoy with corn on the side.