1 hour of work per month, $100k per year, each hour of his time was worth nearly $10k. Cool story but I never would have sold. This is the ultimate side business.
He has 0 risk once his check for $500K clears. Every month he keeps the app there is a risk that something goes wrong; and that 1 hour a month probably doesn't include time that is spent thinking about those things going wrong. Getting the money all at once reduces his ongoing cognitive load.