Are certificates of occupancy required every time a house changes ownership?

Is a certificate of occupancy required for turning on utilities/moving in to a previously vacant REO or foreclosed property bought through a wholesaler using cash and/or private funding? I'm not sure who would require such a certificate, so asking if or when such is required for an owner occupied single family home.

I'm not planning on using conventional financing, getting a bank loan, or buying a fire damaged property, abatement issues, etc. Basically looking at what would probably fall in to a flip or rehab category, but something just this side of habitable (loosely speaking), to fix it up while "living" in it off and on until ready for moving in all belongings, appliances, pets, etc. permanently.

The posts I've read state that the seller is not responsible for this & that's fine by me, but I'm naive as to why it matters and can't seem to find under what circumstances the certificate is required OR who asks for it. 

TIA for any help understanding this :)