It depend the mold existing there when move in

or generated after tenant move in. Also depend on your local property code.

In Texas, you can search Texas property code in Google and find the original code. It is not hard to read.

Also depend the lease agreement, if it require the tenant report any defect to landlord in writing.

I always send a book about mold and a book about lead to the tenant when lease signed. And in lease, I stated the landlord/property manager did not check the property and the tenant inspect the property and accept the property "AS IS".