Ok, This is a very simple setup.

First you need to buy up all the shops you can (since you don't have to repair them) now when your ready to go to bed go to a JOB spot like pie making or etc... start the job and walk away, go to sleep... (Its best to have your controller plugged in to your console your your controller will not die) when you return you'll still be FAILING the job your started but you will have gained your shops profits every 5mins. - ENJOY!