Backing all these comments that say it's about communication. If I found out my partner has been selling nudes, hiding it from me, and also hiding the money? An unforgivable betrayal of my trust and our relationship. If he came to me beforehand and we discussed it and the money went towards our mutual goals, it would at least be something I'd consider.
The whole point is not hiding it from your partner. Discuss things before you do them.