I started my Commercial Digikit design business 'Algera Designs' nearly two years ago.
My advice for anyone starting out is to Research and network as much as possible...
Have a Blog & or website/ Facebook/ Pinterest etc...
Consider selling through a store as the initial outlay is lower this way. They take a commission on your sales.
Layouts and ideas are all important... I love to be inspired as to how a kit can be used.
Spend time at various Scrapsites get involved.

Starting any business (self employed) does require lots of your time, some financial outlay and most of all a Passion of Creativity to carry you along the journey x

*Would love to see more tips, advice and insights added to this topic by other Designers / CT people etc...