Hello,
Here is a nice flat in Paris for your vacancies this summer. It's a typical old flat in paris : 1 room and 1 living room. There's one bed for 2 persons but you can easily be 4 persons in. It's located near Gare du Nord, Gare de l'Est and Parc de la Villette, Parc des buttes Chaumond.
You'll see more details on the website:
rent-in-paris point org
Vincenzo