Note: I wrote this answer on Quora and then said, hey, let’s put this on the blog too.
What does it mean if I have 4 planets in the 9th house: Sun, Mercury, Venus and Mars?
I cannot give you a complete answer because I do not have your chart (and please don’t put it up or give me birth info, because I don’t read individual charts on Quora.)
The ninth house rules publishing, teaching, law, and travel. The zodiac sign that rules the 9th house is Sagittarius. Even if your sun is not in Sagittarius, you’ll share many of the attitudes and traits of a Sagittarian individual. You may be gregarious and the life of the party. You may impress many people for no damn reason at all, and know too much for your own good. Endlessly optimistic, you’ve lost more than one lover because of your fearless cheeriness in the morning. Don’t worry. There is always another.
Publishing, teaching, law and/or travel play a prominent role in your life. You may find you end up in more legal troubles than the average person, again for no damn reason other than the Universe seems to have it out for you, or it just wants to test your ability to act as your own lawyer. Remember what they say about who is a fool in this instance.
You’ll be a teacher one way or another. Either you are a teacher, teach some sort of class somewhere or coach kids. You love kids, someone else’s that is. But if and or when you have them you’ll spoil them rotten, much to the consternation of the other parent.
Secretly you dream about being a great writer. However, writing is hard work, so unless you have some grounding elements in your chart, you’d rather have someone else write it. You are the person who walks up to a writer at a party and says, “I have a great idea for a book. Why don’t you write it and we’ll split the profits?” This is why writers drink so often and have lawyers on speed dial.
You love the idea of travel but you may be a poor traveler. However, that doesn’t stop you from dreaming of exotic climes. You love all kinds of maps, even that funky one drawn by J.R.R. Tolkien’s son, Christopher, from Lord of the Rings. You even know that’s who drew the map. Secretly you want to be an elf.
When the Temptations sang “Papa is a rolling stone,” they were talking about you. Hey, at least you’ll gather no moss.
Disclosure: I have two planets in the 9th house, which gives me license to poke fun at people with a prominent ninth house. 
If you want to see more of my answers to astrology questions on Quora–Click this link.
Thank you for dropping by and reading.