Can't say I know a lot about Army, but I'll tell you what I do know. No monies will start until you contract and you won't contract until you pass the PFT (or whatever Army call the physical fitness test). So you want to be in shape to pass it right out of the gate the first week. There is NO chance of them picking up room and board as well as tuition, but it's my understanding you can have them pick up room and board INSTEAD of tuition. If you have other scholarships that will cover tuition this might be a good way to go. However, there are schools that offer free room and board to ROTC cadets. I think Texas A&M is one, but I know there are others. You should ask admissions at the schools about this. Money wise I don't think there is any difference between the 4 year and the 3 year AD. There MAY be a difference in terms of your service commitment but I really don't know. This is a great question to ask on the forums by the way. You'll get input from people a lot more expert than I.