Online Businesses

Personal online businesses have been popping up all over the place, and I was wandering what everyone thought about them. One of my close friends actually just quit his job, and is starting his own online business. Some people say that there is money in online businesses and it is the way to go to make money. Is starting an online business worth the risk of quitting your full time job? If so, why, and what sort of benefits can come from starting a personal online business.