Be very, very careful in the crucial beginning stages of your business about taking on fixed overhead. Do you need an office or can you work from home? Do you need an employee, or can you do it on a computer, or have the work done on a contract basis from online sources? Do you need a big advertising budget at the beginning? Do you need expensive resource materials or can you look it up on the internet? Do you need a new computer or can you use your old beater laptop?
There's the old adage that you have to spend money to make money, but be very careful about the money you spend and also be careful about taking on costs that you'll have to pay on a monthly basis.
If you're not careful, you can work your butt off just to pay your bills and not have any money left for profits.