Bday cake?

Is a dense cake or a light and fluffy/somewhat crumbly cake good for a bday cake to sell to someone 4a party?
which cake should I make? I was going to add half and half in the batter along with some sour cream. is that a good idea? thx

The name of the game is supply and demand. When you're selling a product, it needs to be what the buyer wants. If it's for a specific buyer, ask about their preferences and sell them a "custom" cake that is exactly what they want. Also, do some market research. What are your competitors selling? What can you make at a profit? What can be your "signature" cake?