I remember realizing this at about 20, and that if I bought my own cake ingredients I could make cake for startlingly little money. The most expensive part was probably the ready made frosting.

Anyway I started making cakes for friends and neighbours in my apartment building after work. I didn't keep it up for very long, maybe a year, but I'm convinced my reputation is still riding high, decades later, from the goodwill I sowed during that time.