Well what kind of publishing company are you talking about, Ebooks or actual physical books, or both?
Anybody can get books printed, all you need is money, distributing them is what takes the effort and planning. Obviously distributing things electronically is a lot easier than putting them on shelves. I have started a magazine publishing company, but not a book publishing company, and it took us 4 months from moving into the office to having our product on shelves. But that was 5 people working flat out day and night, with a solid plan.
It's a pointless question really, you need to sit down and just work out a plan, that will tell you how long it is going to take.