Hey guys,

I'm in Paris researching at Ecole Centrale Paris. Although Centrale has a housing they give priority to their undergrad students. So, if you are a post-doc or Ph.D. student you might have troubles with housing.
The city of Paris may is the most difficult city to figure out a place to live. Although there are lots of student houses spreading over the city, depending on the season you are coming and when you have done the reservation, you will be able to have a plenty of difficulties in having a place.
I would say to focus on student houses in advance. The best place is Cite Universitaire http://www.ciup.fr/, where you should apply by this website. Maybe other options could be interesting as well such as ALJT http://www.aljt.com/ and even CROUS http://www.crous-paris.fr/.
I really point out that renting an apartment is pretty difficult and requires a plenty of patience and lots of documents and French sponsor.
Although the rental prices are quite expensive, depending on your place you're able to apply for receiving CAF (www.caf.fr). It's a government cost help for housing.

I hope it's helpful.

Cheers,
Carlos.