One person signs the lease
As for concubinage (« union libre ») the lease may be signed by a single member of the couple. Those who signed the lease
awarded the title of "tenant".
His/her partner nevertheless has some protection in case of abandonment of housing or death certificate, it will be easier to stay in the home.
But, having signed a PACS also creates obligations. Indeed, the signatories of a PACS are in solidarity for their housing expenses ...
Depending on your income, each tenant may be compelled to pay the rent until the dissolution of the PACS.
If the signing of the lease leaves
As for concubinage, if the signer of the lease leaves the housing after a notice period, the partner must also leave the shelter, except if the owner agrees to make him/her sign a lease on its behalf.
Departure of a partner who has not signed the lease
He / she is free to leave but remains financially responsible until dissolution of pacs ...
Both partners signed the lease
The rules are the same as for the « concubinage » and « union libre » with the difference that you are financially responables even if there is no solidarity clause.
If you contact your Caf for possible financial assistance, both of your income will be taken into account.