If your concern is lack of space, in most cases it will be less expensive to add on to your existing home than move to a new house. There are also some intangible factors that can come into play. When living in an urban environment, one can appreciate the value of good neighbors and you may not want to move away from your friends. Schools in your district can also be a deciding factor for staying in your current home.
We can help you do a cost assessment to see if this is the best solution for you.