I have posted numerous comments on AAM regarding leaseback. To summarise: poor investments because poor areas. Leasebacks aim to artifically fill a 'shortage' of holiday accommodation in an area.
Alternatives to leaseback in the South of France can be divided by rental options: long term or holiday lets.
The former offers security as the tenants are vetted and the market is very strong. France has a strong rental culture. Insurance against non-payments by tenants can be bought for 8% of the rent - this acts as a type of guaranteed rental.
Short-term/holiday letting has potentially much higher returns. Rent per week is generally the same as rent per month on a long-term contract. But you will only get these returns in an area with strong demand. And not all of the South of France has strong demand.
This option has the great benefit of offering owners the opportunity to use the property themselves when its vacant.
I have an estate agents in Nice. Contact me if you're looking for advice in this area.
My website has a fairly detailed guide to rentals and investments too.