I think one problem facing property owners who rent out for weekly holiday periods is where to advertise and spend your money on marketing as there are so many rental websites springing up.
There are some good major sites that allow you a link to your own website and I always recommend typing keywords in google to see who comes up on the first or second page (not the paid ads on the right or highlighted at the top) ie: holiday, villa, apartment, rental, rentals, spain, direct, directly, owner, spain