I am a sub contractor I did a job for a homeowner he paid the full amount after I sent a notice. He is now asking me to come back and do additional work at my expense. And threating to leave a bad review on yelp,google etc. He paid in full and right after asked me for advice; now 3 days later, he is making threats for me to do work that was not on the contract.
Legally speaking, if you fully performed the terms of your contract, then you have fully satisfied your obligation under the contract. If the homeowner wants you to do additional work, then that should be set out in a new contract. If there is an error or issue with a bit of contracted work, you should fix it/correct the issue. But, if the work you performed was satisfactory, it sounds like the homeowner is simply trying to extort free additional work on threat of a bad Yelp review. How to respond is a business judgment on your part. In these cases it is always wise to create a paper trail/save all communications/documents in case a CSLB or legal claim is subsequently made. You may consider telling him, in writing, that as you have fully and satisfactorily performed all obligations under the contract and have been paid in full, your contract is complete but that you are happy to provide him a quote for a new contract for the additional work he is requesting.