The main downside to starting full time is risk. If you jump ship and leave your job,you risk loss of current employee benefits and have no guarantee of steady income, contributing spouses or partners excluded. The upside to starting off full-time is potential rewards, including the opportunity to make more money than you can at your current job, and to gain control of your future. Your decision to operate your new business on a full-time basis will largely be determined by your current financial situation, your own risk-reward assessment, and your goals and objectives for the future. Jumping in full-time will appeal to the true entrepreneurial mindset--people who perfect to blaze the trail rather follow behind in the wagon train.