I could build a house. With zero experience you can find a job in house building as they will pay you to learn on the job (depending on the economy you might or might not be able to find such a job today, in good years they will hire anyone who isn't disabled - but there are bad years). Many people who have never had a construction job build their own house (only a tiny %, but that is still a lot of people)

I suppose I could work on a cancer cure. However since I don't have a background in biology I would have to pay for several years of school to learn the required skills. Those classes are hard and there is no guarantee I will pass (I have an engineering degree, so my odds of passing should be above average).