I saw the beginnings of bud formations at about week 2-and-a-half weeks, with my indoor plants. But every strain is different.
Almost every Kush strain I've heard of, was Indica dominant, or 100% indica. This means, when the bud starts comin', it'll come FAST! You should be ready to harvest your smoke in 2 to 3 months, as most indicas bud fast and finish early. To help you harvest at the perfect time, you'll need one of these.
http://www.radioshack.com/product/index.jsp?productId=2179604 This Illuminated Microscope allows you to see when your trichomes are at their perfect milky or golden ripeness. Your gonna' want to start checking your trichs in about 6 or 7 more weeks.
Hope this answers some questions, bra.