The location is incredible. You can walk to the Notre Dame in 5 minutes and Louvre in 7 min. Just downstairs on the street, you'll find lots of cafes and restaurants, and several Metro/RER stations, which can take you anywhere in Paris and the CDG airport.
The apartment is on the 5th floor (6th floor if you're from the US) and has a small elevator, which will literally save your life if you have several large baggages. The whole apartment is sparkling clean and Liliane takes great care to maintain it in a perfect condition.
You will get your own bedroom with a double bed (full size in the US) and your own bathroom (no toilet). You will need to share the toilet room, the kitchen, and the living room with the host.
If you plan to take RER B to CDG airport, be advised that there are two RER stations (B and C) near the apartment building. RER C station (this one does NOT go to CDG) is right at the bridgehead.
You need to walk on the south side of the Seine river toward Notre Dame for about 3 min, and then you can find the sign for the RER B station on your right, just at the end of a narrow alley. Actually, that is the entrance to the elevator which brings you down to the RER B station underground. You can reach CDG by RER B in about 40 minutes. You can buy an Airport-only ticket for €10.50/person.