If you plan to spend a few days in Paris and are on a tight budget, you will soon find out that there is not a large choice of affordable accomodation. Hotels with prices under 80 € a nigth are hard to find and appartment rentals are not suited for short stays. There ARE cheap hotels in Paris, however, with prices starting around 40 € a night, but you will need to make some concessions.
There are several hotel chains in France, with every pricing you can imagine. Some of them are very affordable, with prices for one night starting at around 35 €.
These hotels are generally reasonably modern, well maintained and offer easy online booking and payment. The main drawback is that they are more designed for sales representatives than tourists. They are generally located outside Paris in cheap or noisy areas (near the peripherique or near airports) and totally lack charm. I have tried hotels of the two chains listed below.
Hotels Première Classe
These hotels are part of the Louvre Hotel Group.
Prices: 36 to 48 € a night
None of these hotels are actually located in Paris. They are all in the suburbs.
Online booking and information at www.premiereclasse.fr
Also check the other chains of this group, especially Kyriad hotels.
Etap Hotels
This chain is part of the Accord group
Prices: 43 to 52 € a night
The hotels are closer to Paris.
Online booking and information at www.etaphotel.com