I have played this game through once, and noticed that I often struggled with being able to add new services to shops. They often said "Hard" or "Very Hard", and I know that in other Kairosoft games, you can trigger different things to make this type of thing easier. Is there a way to make adding services easier, so I don't keep wasting hearts trying to do it over and over again?
As your store increases in level the difficulty goes down.
Also, sometimes if the store has been in operation long enough it will prompt you to add a new service for 1 heart. But I have no idea how to trigger that condition manually.