Will homeowners insurance pay for mold removal hidden under paint on ceiling of covered porch there at the time of purchase?

You'll have to refer to your policy language or consult with your agent. Most homeowners Insurance policies offered since the late 1990's automatically exclude coverage for mold or fungi and relegates back to a home maintenance issue.

Also note the pre-existing conditions clause in your Home policy.

The home Warranty purchased with most homes new and used, warrant property condition at the time of delivery.