So I'm told that I earn money by building stores in my settlements. They cost a pretty penny/cap, though. How fast do I earn money from these stores and what are the conditions? And do I need to check back to collect on the earnings?
A 300 cap store tends to see 25-30 caps per day in income with a moderate Charisma score and no investment in anything that may raise the amount of caps earned. That puts the ROI at about ten in-game days or so for the basic general store. However, bear in mind that stores also increase the happiness of settlers which has a different kind of game value altogether.