The biggest benefit to buying an existing home is how quickly you can move in. In the case of buying an older home, you need to take into account the age/condtion/lifespan of things like windows, mechanical systems, appliances, etc. as those will likely be costs to consider in the near future.  Building is a time and financial commitment that has huge benefits but definitely comes at a cost... think of it like playing the long game. In the end you might determine that the benefits of living in a home with tons of natural light and a layout made for your lifestyle is worth the wait. Never underestimate the mental health aspect of a well designed home.