"You want a horse."
Translation:Tu veux un cheval.
It should be 'voulez-vous un cheval?' but yes you can (or Veux-tu un cheval?).
There are a lot of ways to ask questions and the inversion is the most formal and the least used. It is more common apparently to simply say 'Vous voulez un cheval?' and raise your voice at the end which makes it a question.
Or you can also say 'Est-ce que vous voulez un cheval?'.