Building Permit for Tiny House Needed?

Hello,

We are buying a property of about 3000 square meters in a small village in the Yambol region. There is an old house on the property which is basically a ruin though. Since the house is too big for us anyways, we want to tear it down sometime in the future. We want to place a tiny house (on a trailer) on the property. Does anyone know if a building permit is required for this? The house would not have a foundation, since it's standing on a trailer. In many countries, they don't require building permits for these houses but we want to make sure that we don't get into any trouble with the Bulgarian authorities. It would be great if someone could give us a tip regarding this.

Thanks guys!