To dream of a mansion represents your perspective on a situation where you are all-powerful, more resourceful than others, or experiencing better success than others. You may feel better, luckier, or more capable than other people in some way. You may have a sense of something wonderful or special happening in your life. A perspective on a situation where you feel it's impossible to be perceived by others as losing.
A mansion may also reflect feelings about how exceptionally resourceful, creative, or powerful you are. Feeling that big achievements or adept skills are always easy for you. Feelings about being a leader, boss, or head of the family.
Mansions in dreams may also reflect your feelings about people in your life that you feel are too powerful, too important, or resourceful to ever be forced to listen to you. Someone in your life that enjoys more power than you of which you can never stop. Possibly a reflection of your feelings about your boss. Feelings about someone in your life that never loses.
Relationship wise, a mansion in a dream may reflect feelings about being noticed by others as having a perfectly happy relationship that is impossible to breakup. Feeling that you are perceived by others as having a lucky perfect relationship with a "soul mate." Relationships where you feel you are a "show couple" or "power couple."
Example: A young man dreamed of being inside a beautiful mansion and being surprised to find out that he owned it. In waking life he had discovered that he had natural talent for art that was better than average people. He was shocked by how exceptionally talented he was. He couldn't stop drawing pictures that impressed people.
Example 2: A young woman dreamed of seeing a mansion that was run down on the outside, but beautiful on the inside. In waking life she had told her boyfriend very painful truths that caused damage to their relationship and feared a breakup. The mansion with the exterior damage and beautiful interior may have reflected her feelings about herself being perceived by others as having to accept flaws to her reputation for having a perfect relationship that was originally perceived to be too good to ever break up. She would have to accept being viewed by others as having a strong relationship without an appearance of perfect happiness.
Example 3: A woman dreamed of walking into a mansion. In waking life she tried to talk to her boss on a personal level, but her boss had no interest in talking to her at all.
*Please See Houses