My friend and I just planted a seed two weeks ago. It sprouted. But he wants to know how long it takes to fully grow the plant, and like when the buds come and how big it will be in a month?
TBH, those are some questions you need to figure out yourself, it's a matter of preference/strain really. Typically, it takes about 4 months depending on the strain, and again, depending on if it's indica or sativa dominant you will want to trigger flowering at different times. Sativas you can almost trigger flowering right away, where as Indicas will need 3-4 weeks of veg time to bush out well. To answer that last question, it should be close to a foot tall. Then in flowering it will double or even triple in size.
Read some of the stickies. Start with Grandpa's Grow Guide. It will answer all of these very basic questions. Good luck.