I'm doing this. Just from my personal experience, I started trading as a way to make money from home because I got married and had three kids close together, so I didn't have the option to go out and work. My husband has a good job and we make good money together, but have a lot of bills as far as a mortgage, two car payments, a loan, etc., so I decided to continue trading and use some of that money to start another business.
I've always heard that wealthy people get money from multiple sources, so I think it's a good thing to have income streaming in from different projects and things.