Furnished or unfurnished?
In France, there are two types of letting investments: furnished and unfurnished. The letting of an empty apartment is established by a lease of three years, renewable.
This type of contract allows the owner to reacquire the property at the end of a three year contract and for distinct reasons. The lease "unfurnished" is regulated by law and your yield is between 3% and 3.5%, after taxes.
If you want to let a furnished apartment, the lease is one year. The length may, however, be less and the property may be a primary or secondary residence.
In the case of a secondary residence, the owner is free to set the amount of rent, taxes and length of the lease, which offers the owner great flexibility. In this case, the yield is between 7% and 10%.