Although my dream home - and many people's dream homes, come to that, are *new* homes, it's always possible that you can find your dream home in one that already exists, one in which someone you respect or admire used to live, for example.
Of course if it's a "big" someone, like Edgar Allan Poe or Walt Disney or someone, any home they lived in has been turned into a museum if it wasn't destroyed in renovation projects over the years, before towns realized that people would pay to see homes in which famous people lived.
But if the past person whose home you find is famous only to you... then it might still exist and you might still be able to buy it.
I'm interested in women's aviation...wouldn't mind seeing the homes of Ruth Law, Phoebe Omlie, etc. Amelia Earhart's home has been turned into a museum, but she's probably the only female aviator whose home has received that distinction.
There are a few companies that are ancestry researchers, and will do your research for you to compile a family tree book. Turtle Trove ancestry is one of these.
If you have them do research back into your family tree, who knows what ancestors you might not uncover...and learn where their homes were and if they're still standing, too.