Is some sort of mold inspection required

Arrow will treat and give you a certificate for under $500.

If you do get certificate make sure it is legit. There are licensed inspectors that will come out and test moisture through out the home. They will also take numerous samples and send to a lab for mold tests, etc. I know one reputable inspector that is offering this service at $650 and provides basically stamp of approval you can close in the walls.

Good to have when selling to prove everything was done right. Keep all receipts, paper work, etc through out the whole process to present to potential buyers.