Rahu, the demon God, known as north node of the moon in western astrology is a mastermind planner, magician, illusion, mass communication, the extravagant show off guy who wants everything now and wants it with huge amount, foreign desires, foreign things, exotic things, scientist, computer and corrupt.
When one runs through the mahadasha of Rahu which is 18 year old time period, one can surly be lost in life and may not know which direction their life is headed. There is a fog in front of them where right things looks wrong and wrong things look right. This is why it's very easy to get into drugs, alcohol, gambling and unnecessary worldly desires while losing one sense of dharam. The native can run into to people who are not what they seem and may swindle or cheat the native out of everything they have. The desire to succeed amplifies and desires to get all the material gains increases within the native, especially if such mahadaha occurs in 20's. It's always better to have Rahu alone in your horoscope during his activation of mahadasha. Anytime Rahu associates himself with another planets he takes away the energy of that planet and sucks it dry. However, if Rahu is well placed through friendly signs like Taurus, Gemini, Cancer, Virgo, Libra, Capricorn and Aquarius than there would be gains in material wealth, comforts, sudden marriage, sudden foreign travel or permanent settlement aboard. Yes, Rahu does well in the sign of Cancer, even though it's ruled by it's enemy Moon. The native can also go towards computers or computer engineering, medical field as Dr. Deepa Chopra become a doctor during his mahadasha of Rahu and came to Untied States. If Rahu is in 2nd, 3rd, 4th, 5th, 7th or 10th house while in Venus or Sun sign then it can make a person want to be a movie star, or become a well known celebrity. Rahu desires fame, especially in the sign that represents fame.
As far as conjunction is concern, Rahu with Venus, Mercury or Saturn can give huge amount of wealth and fame, especially when with Venus it amplifies the qualities of Venus like luxury, wealth, beauty, relationship, lust and art. People can suddenly have kids or might have kids outside of marriage during Rahu's dasha if Rahu is sitting in the 5th house. The native is never satisfied during Rahu's dasha no matter how much they get, and they can't get enough. Anywhere Rahu is placed, things related to that house will be the front most important part of the person's 18 years dahsa life.