Rarely in life do things go as planned, especially in real estate.
In a perfect world, when buying a new home, most people want to take possession of their new house before having to move out of the old one. This makes moving a lot easier and allows you time for painting or renovations prior to moving into your new home.
Where it gets complicated; most people need the money from the sale of their existing house to come up with the down payment for the new house!!
This is where bridge financing comes in.