A brief survey shows that Centrale Lyon students have a preference for certain parts of Greater Lyon.

Within the city of Lyon itself - sought after for all that goes on there - you find a particular concentration of Centrale Lyon students in the Terreaux district, where rents are not too high, and the large number of relatively cheap little restaurants and bars form a special attraction, ensuring a lively atmosphere all the year round. On bus-lines 19 or 3 (from the Hôtel de Ville), the School is just 20 minutes away. And this area is also at the bottom of the famous slopes of the Croix Rousse hill, with its traboule-passageways, artists' studios, exhibition places, etc.
see http://www.lyon-les-pentes.com/

Also in Lyon, the Perrache area (including the eponymous railway and bus station) has affordable rents, and is obviously more than central transport-wise: 20 minutes from the School by the 44 bus (from Perrache bus-station), and 2 hours from Paris or 1? from Marseille on the high-speed TGV train.

Outside of Lyon itself, Centrale Lyon students tend to go for the town of Tassin la Demi Lune, which lies on the 55 bus line, halfway (=10 min) between Lyon (Perrache) and the School. Bus lines 42, 14, and 73 also run there, making it just 5 minutes to the Gorge de Loup metro/bus station, which is an important node in the TCL (Transports en Commun Lyonnais public transport company) network for the west of Greater Lyon. Choosing Tassin is choosing comfort, with the many shops and services, peace and quiet, simplicity (no need to run the risk of taking the notorious Fourvière tunnel every morning!).  Rents there, however, are higher than in Lyon itself.

Ecully itself is also a favorite, being close to the School, and a pleasant place to live, with a hypermarket and 86-shop mall, plenty of shops downtown, banks, cinema, swimming pool - and yet still with a village feel to it all. Rents in Ecully are high. 
see  http://www.ville-ecully.fr/

Flat-sharing is a solution students tend to like -but to which, unfortunately, the rental agencies are less favorable. There is a web-site dedicated to the subject, which students have found useful:
see  http://www.colocation.fr