Guys in porn:
1. Get hard under any circumstances (the girl might be a minger).
2. Stay hard for hours while being directed, and told to change positions.
3. Don't cum too early. Cum exactly on-demand.
4. Unless you make it pretty big in the industry, earn pretty well peanuts (the girls earn the money).
5. Be prepared for everyone you know to find out - friends, work colleagues, family.
Still fancy the idea? It ain't for the faint-hearted.