For an online business, a detailed and in depth business plan is usually not necessary unless you are trying to combine your online business with a traditional business. For most online business startups, the detail involved with planning a traditional business is not required. However, it would still be beneficial to you if most of the topics were still covered, even if only briefly. Having a written plan in front of you will help you to focus on important aspects of the business.
Now, in addition, when you know the average number of transactions per customer and you know your average dollar sale per transaction, you can also project how many customers you would need over those 10 years as well. This would tell you everything about what your business would need to do to give you the salary you want. So, wouldn't it be nice to see what a plan like this would look like? Could you do it? It might not be as tough as you might think.