Start with one question: does the bigger home you want actually exist, at a price you can carry, in your target area? If it does, buying the space is usually the smoother path. An addition means design, permits, material selection, hiring and riding contractors, and absorbing the overruns that tend to come with construction. Historically it has often been cheaper per square foot to add space than to buy a home that already has it, so the addition can win on pure cost. Most people just aren't set up to run a construction project, and the aggravation and risk are real. Your current mortgage is the other half of the decision. If you hold a low fixed rate, moving means giving it up and financing the entire new purchase at whatever rate is available. A HELOC keeps the low first mortgage in place and borrows only the improvement money on top. So weigh the cost and hassle of building against the cost of trading away your existing rate, and pick the path that fits your tolerance for managing a project. This comparison is exactly what the free Roadmap conversation (about 20 minutes) is built for: we run your real numbers on both paths.