You have to do a business plan. This is not a "slapped together" document. If you go after business loans, they will ask for one, PLUS it is a great exercise. Mine took 9 months, a CPA, and attorney and an orgz that specializes in helping people put biz plans together .... it ended up being over 40 pages.
Start there. In it, you will be asked to research your business market, your local market, your target market, who is your competition and how you will deal with that, a break even point is a required part of the plan (that's why I got the CPA involved), sales projections, sales history (if you have any), your resume, assignment of duties in the business, will you have an Advisory Board and if so, who are they and how can they help you in your business, estimated monthly costs of operation - rent, utilities, loan payments, payback schedule, phone, advertising, payroll, insurance, company car (how will you deliver?),
Just off the top of my head ......
If you are considering operating your business from home, check the 'States that License Home Bakeries' thread at the top of this forum (link below) to see if that is legal in your state. 
http://forum.cakecentral.com/cake-decorating-ftopict-32550.html
Quote by @%username% on %date%
%body%