Server bills - they get VERY expensive after a while
That's something else to be very aware of when runnig your busines, if you do not pay the bill, you put all your customers in jepordy. Some people when starting out can skip on a bill for say electricity or whatever, but if you're a few days late with hosting, you can cripple your business.
Having funds to operate for 2-3 months with NO income is almost a requirement.
One very important thing that you mentioned Lesli was the spearation of business and personal - and even to the extent of personal LIFE. When starting out, every waking minute of every hour will be spent building the business. And then, once it's going, every minute will be spent working
15 years in this business and I still rarely take a vaction.