Some traders do it as a full-time job because they have become professionals in the business. It will be risky to resign from work to become a trader when you are not sure that it could replace your job financially. It will be safer to venture into trading on a part-time basis until you are sure that it could be your main source of revenue.
There have been cases of people selling properties or taking loans as trading capital. This action should be discouraged because trading is highly risky. It is better to invest what you can afford to lose or what you can live without.