Whoever is seeking to file a petition or counter petition would fill out the affidavit of indigency.... because that is the person who would be requesting a waiver of court costs.  In your case, your husband as the petitioner would fill out the affidavit.You don't need to file a counter-petition as the respondent, but if you do, then at that time you would also need to fill out an affidavit of indigency.  You do not need to complete one if you are only going to file a basic answer or waiver of service.