If each ad is small and contains only information about a single object, I would model this as a named entity tagging task.
If you have ads which refer to several items to be sold, you would have to disambiguate which property belongs to which object. Dependencies would be one way of modelling that.
In my experience, the NE setup is much faster to annotate with.
You could also ask annotators to reject ads which contain multiple objects and then funnel the rejected examples into the more complicated dependency formalism.