A lot of people have great ideas, but when do you know if it makes sense to start a business?
I found a great video that answers this question.
How would you answer the question?
You know when it makes sense to start a business by creating a business plan. Start with one that's just for your personal use.
Here's an article to get you started: http://articles.sitepoint.com/article/business-plan-wont-sit-shelf
There are also some great resources at the SBA: http://www.sba.gov/smallbusinessplanner/plan/getready/index.html , at the Business Owner's Toolkit: http://www.toolkit.com/small_business_guide/sbg.aspx?nid=P01_0000 and at Entrpreneur http://www.entrepreneur.com/startingabusiness/startupbasics/index.html
I think the time is now, depending on what you want to do and how long it will take to break even. If there is a demand for it, and you know how to supply it, then go for it! You can always hire people to do the tasks that are technical and more important for day to day functioning.