Air France bus
Line 2 goes to the Place Charles de Gaulle (Arc de Triomphe) and Porte Maillot (in the La Defense skyscraper district). Buses normally run every 15 minutes from 5:45 a.m. to 11 p.m. The fare is 15Euro one-way or 24 Euro round trip, with children 2-11 paying Euro 7,50 each way. Trip time: 35-60 minutes, depending on traffic.
Line 4 serves the Gare de Lyon and the Gare Montparnasse. Coaches normally depart every 30 minutes from 6:30 or 7:00 a.m. to 9:00 p.m., and the fare is Euro 16 one-way or Euro 27 round trip (Euro 8 each way for children). Trip time: 45-60 minutes, depending on traffic.
Air France also has a Line 3 bus that runs between Charles de Gaulle and Orly Airports. Fare is Euro 19 each way for adults and Euro 9,50 for children, with no round-trip discount.
After you've retrieved your bags and gone through customs, look for a "Gare" sign with a train symbol. (CDG has two RER stations: one for Terminals 1 and 3, and the other at Terminal 2.The terminals are connected by a free CDGVAL shuttle train.
Both shared and private airport transfers are offered and booking can be made thru this site while booking the apartment