I'm guessing you might want to look into Horary
or Electional Astrology. It is used when you wish to ask a question, such as, "Will we purchase this house?" You write your question down, note the time and then cast a "natal" style chart for the moment. Then you interpret that. It's similar to natal astro, but there are some key differences. Google "horary astrology" or "electional astrology" to see which one would fit your needs.
Off the top of my head you would want to avoid times when Mercury is retrograde for signing contracts, and also any time when the Moon is Void Of Course.
Good luck and Happy Home Buying!