Those who let out cheap digs in their own home are exempt from income tax and business rates.
The accommodation must be the principal home of the tenant, and the annual rental must not exceed a rate of 167m2 in the Ile-de-France, or €121m2 in the provinces (2008). These maximum rents are adjusted each year
Thus, for a room measuring 20m2 in the provinces, the rental cannot exceed €2420 per annum, or €201 per month.
These maximum rents exclude other charges that may be payable e.g. meals, laundry.