What a great question! I see a business idea like a seed and depending on the kind of seed, it takes different time and strategies to nurture it successfully. The important key is not how long, but how committed the entrepreneur is willling to be, which will determine how far the idea goes. A seed typically goes through this cycle: Plow -> Plant -> Nurture -> Harvest. For the entrepreneur it looks like this: Idea Development -> Selling the Idea -> Testing the Idea -> Evaluating/Enjoying the Results and the cycle begins again. This has helped me see entrepreneurship as an ongoing discipline/passion and let the "how long" question take care of itself. Hope this helps!

Document your idea and refine it - try test with some potential client for feed back. Network a

In my experience, it may take at least 4-6 month to preapre a proper business plan (i.e. Plan, ask for advice n feefback, revise n revise...). While doing the plan, you should define clearly n HONESTLY what resource ( money, infrastructure, people..) that the business need and what skill / knowledge u and the team need. Then based on that u would know how much time u need to get all these preparation together. Of course while preaparing, keep yr eye and eye open, so that u keep fintuning the idea. When everything ready, opportunity would appear even before u know it:)