Hi Jurgen and Ingrid,
If you look on www.libercasa.com and search for Tivenys, i have advertised some properties for local people without them using estate agents because of the large commissions they add onto the price. I actually live further up in the hills in Corbera d'Ebre, but a really nice Dutch guy called Peter is reforming a house on his finca to use it as a casa rural. If you speak Spanish or Catalan, you should'nt have a problem finding work.
When you come over i'm sure Peter wont mind you going to look at his place, and he was a constructor in Holland, so he can give you lots of useful information. I know prople in Tivenys who were allowed to double the size of the house on their finca, which is pretty good compared to some villages.
Hope all this helps.
Julie