How to get removed as a co-signer, FHA?

I am going to be co-signing on an FHA mortgage very shortly to help my parents get a property. I understand there is a difference between a co-borrower and a co-signer. I am going to be co-signing the mortgage, not co-borrowing. The only reason I am co-signing this loan is because some unforeseeable circumstances came up that were causing my parents to get approved for the loan. In the end if they were to be declined a lot of money would have been lost because they won the house in a bank auction.

How long could it possibly take before I could be removed from the mortgage? There is some debt that needs to be payed off on my parents part, which was the only thing keeping them from securing the mortgage themselves.

Also how much can this decision effect my credit? I know it will go down, but once my name is off the mortgage will it return to the way it was before I co-signed?

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