This could be a simple anxiety dream or it might involve something a little heavier, like depression. As the dreamer, you should always follow your own feelings to the meaning. Since the dream was frightening for you, it tends to indicate something unpleasant. This could be your beliefs about something or something you're currently facing. However, it could also represent the unknown and the fear of exploring and knowing yourself on all levels even if that includes facing all of your demons. An old house can indicate an old way of living, like returning to your past or exploring that more in depth. Floating is generally an indication of effortlessness. You're able to move with little effort. It also indicates subconscious exploration and possibly out of body experiences/explorations.