I've joined a league where you draft 6 AAA players, 2 pitchers and 4 position players.  The commissioner didn't know the answer to my question, so I'll ask it here.  I've drafted 7 MLB players valued at $200,000 apiece.  This way I can spend more money on my other 18 MLB players per each player.  I plan to drop these 7 players valued at $200,000 which will give me $1.4 million to spend on the waiver wire.  Then I will promote all my AAA players.  Can I do this?  Or do I need to keep a certain number of MLB players?  There are no PA or IP limitations in this league.  Thanks. 

Do you have to keep 6AAA players or can you drop 3 and only carry three after the start of the season?

The short answer is yes, you can do it.

Overall you have to maintain a roster of (I believe) at least 12 hitters and 6 pitchers.  I'm pretty sure it doesn't make a difference if those 18 players are "real" players or AAA.  But maybe someone else can confirm...