You don't have to complete Greasy Palms.
That's just a side event, or rather, an NTR event.
If you don't pay Agent Diaz on Thursday, Lauren will get her ass spanked.
If Mandy moves into the house later, there's another version of this event.
You don't have to complete all the events; depending on the route, some events will fail, that's normal.
On the Loyalty route, I can't do some NTR events, and on the NTR route, I can't complete some Loyalty events.
It's best to choose one route at the beginning and then play through it.
The Loyalty route ensures that Ryan only has sex with his family.
The NTR route, simply put, turns the women into sluts who hardly ever have sex with Ryan anymore, but instead with Joey and Matt, among others.
After important scenes and decisions, make a new save. If something goes wrong, you can simply load a save game and don't have to start from scratch.