It is plausible in a lot of places, and not so much others. It's very difficult to maintain an underground home. Especially in an environment which is very damp, or "stores water" under the earth. This is why a lot of areas/countries do not build basements in the homes they sell. They're difficult to ventilate, which might lead to toxic/poisonous mold.
But yes, I've seen plenty of natural/underground housing.