Legal Question in Real Estate Law in California

In two sentences, you have managed to raise issues involving landlord-tenant eviction law, insurance law, and the law regarding licensing of contractors.

First, as you note, a landlord must give a tenant prior notice of the landlord's intended entry; reasonable notice is what's required (except in certain cases, including emergencies), and 24 hours' prior notice will be deemed reasonable, by statute, absent facts showing a lesser or greater time would be required for reasonableness.

Second, contractors must be licensed to do most kinds of work, unless the total value of the work falls below a certain dollar amount, in which case an unlicensed person can be used. I believe the dollar threshhold for requiring a license is $500. The penalties for doing contracting without a required license generally fall on the contractor, not the person employing the contractor.

Next, the insurance policy itself would have to be consulted as to what conditions might or will result in its cancellation. It's possible, but by no means certain, that insurance might be cancelled if the insured party (a) fails to perform necessary maintenance, or (b) uses an unlicensed contractor to perform the maintenance.

If you would like a more specific response, please re-ask you question with sufficient details so we can tell what the issues really are.