Installing a skylight is not easy, especially if the roof is not parallel to the ceiling. For a roof that has a slope higher than 6, a professional should install the skylight. Different roofing materials also require varying tools and carpentry techniques. And since a hole will be made on the roof, the surrounding area will be affected, which may not be cheap. Make an assessment and estimate the cost of materials and labor. One might need a home improvement loan, and also check with the local area government if a building permit is required for this kind of installation.