With 'bulking' does come unwanted weight, for the fact that you are taking a 500 calorie surplus to your Resting Metabolic Rate... To minimize that as much as possible, make sure you're working out about 5 days a week, and that your macronutrients are 60% carbs, 20% Protein, and 20% Fat... But no matter what, for the most part you are going to gain... That's why some people "bulk" first, then "cut" later...