You cannot buy beach front condo in Bayahibe or Dominicus, the only one closer to the beach are in Cadaques as Kaki said. There are plenty of condos for sale in Dominicus, about 5 minutes from the beach but certainly not a beach view. You can buy condos in Bayahibe also in the part called Bayahibe Nuevo, but again away from the beach. I would suggest to come and see yourself, plenty of short term or long term rentals. My friend had been a Realtor in this area for many years, so if you are interested, message me and I can get you in touch with her.
Denise