You or the builder should have secured a building permit prior to any work being done. The inspector would have made several visits to the site during construction to ensure the code minimum is being met.
If you do have an insection office, get them in the loop. Best case is that they'll inspect the cottage, give you a CO, and charge you the cost of what the original permit would have been.
In my locale, if you build without a permit, the town can double the fee as a penalty.
Worst case? You'd have to tear open the walls so the mechanicals/elec/plumbing can be inspected.
If you have no inspector or enforcable code in your area, you have what you have. If the place was built poorly, that's your fault for not spec'ing minimum standards in a contract.
Regardless, if you want to insure this place you'll need some documentation for the insurer.
Talk to the town offices, then take it from there.