This is one of those trick questions you may face while attending a job interview. To be frank there is no good answer exists.
You should provide honest answer to such question. If I were you I will say something as follows:
Money is a good motivation for many people. I do enjoy my job but I’ve family and I need to support them.
Non-technical questions help to get more information about candidate. Following are more common question:
What you will do if you don’t get this job?
Why did you leave your last job?
Why do you want to work here? etc
If you are attending a job interview first time use search engine to find such questions or get books from your local book store.
I’d love to know - what part of a job interview question(s) challenges you the most?