Well, in the US at least, there is a homeowner exemption, meaning that you can do the work unlicensed as the homeowner, it still has to be inspected though.
The effective inspection requirements vary. In rural areas outside of city limits (with the possible exception of really wealthy counties) no remodel is inspected ever. In suburban areas outside of city limits inspection is more likely if plumbing or electricity is involved, but is by no means universal. My impression is that most severe problems are caught by the home inspectors that mortgage lenders require.