The core of the game is good, but it needs clearer progression. Right now, it's unclear why I should want to spend my money buying new items for the shop: Do they make me more money? Does it unlock access to new sex scenes? What am I progressing toward? Why shouldn't I just save all my money? (Just being able to click "Whiskey" instead of "Gin" doesn't constitute interesting player progression.)
I think that items should have clearly shown prices, and upgrading to more valuable items thus yields higher profits; and then there should be some kind of reputation system: Serving customers and having better items could increase reputation, while taking a long time or failing to serve customers could decrease reputation. Higher reputation would then translate into more customers and higher tips. (There could also potentially be separate reputation scores for meal service and sexual favors; I could see that working well either way.)