Rahu in 3rd House. 

So, lets see what Rahu can do in 3rd house without any conjunction or aspect from any other planet. 1st lets see what these 2 things represent - 

Rahu represents illusion, foreign lands, foreign things (foreign as in unknown things. So, for someone living in Punjab, culture and rituals of Kerala is also unknown and hence Foreign), Drugs, Medicines, any type of intoxication, fame, wealth, success, obsession, past-life left-over karma, movies, television, online world, cheating, imagined fears, unusual things, unique things, creativity, rule breaker. Rahu also blows things out of proportions. 

3rd house - It is house of your communication skills, neighbors, short distance travels, younger siblings, marketing, announcements, collecting information, hobbies and skills, self-efforts, business, courage etc. 

Aspect-wise, in Vedic Astrology, Rahu has 5th and 9th house aspect. He is unable to impact 7th house from its place as Ketu is sitting there, which is the other axis of Rahu and represents all those things which are non-Rahu.

Rahu in 3rd house makes someone an excellent communicator. They can be fraudulent too in their communications. That's why they become smart salesman, marketing executives and businessman who can sell you anything. They are excellent with their writing skills too. They are very good with creating illusion with their hands, means magicians. They are workaholics. Relationship with younger siblings may suffer due to the malefic nature of Rahu. 3rd house is also a house of ego. So, they can have the heftiest of Ego. 

From 3rd house, Rahu aspects the 7th house of marriage and spouse etc. It shows the need to educate self in matters of business and relationship. 

Rahu's next aspect goes to 11th house of income, gains and network circles etc. So, this aspect of 11th house provides them great income but they need to learn 1st as to how to get that as 3rd house and 11th house both are Upachaya Houses which give them good result only in 30s. 

Again, Rahu and Ketu is only an eclipse and eclipse never last forever, neither in life nor in horoscopes. So, wherever Rahu-Ketu are sitting in horoscope, person realizes the true nature of that house in early 40s, when Rahu and Ketu attain their maturity age. 

Hope it was helpful. Thanks,

Swami Premanand Bharti