Yes, you can get your CFI, CFII, and MEI from another instructor at just about any small airport (FBO-fixed base operator, aka small airport flight school.) The time frame is all dependent on how often you fly and how quickly you can complete one license and move on to the next. You will get at minimum your:
1. Private Pilot
2. Instrument Rating
3. Commercial Pilot (Single and/or Multi-engine)
All previous to your CFI.
I think everyone will agree that if you are looking to make 300K as a Captain of a 747 after 10 years you should move on, that is slightly unrealistic. I don't mean to turn this into a negative thread but if money is your driving force this isn't the profession to choose.
I commend you Rubicon for asking questions and gathering as much information as you can. You can never ask enough questions, I wish 5 years ago I would have asked these questions and not gone in blind.
My two cents is stick with the Business major, see if you like flying and make sure you will want to do it as a JOB and not just a hobby. If you do like it then take the dive and get all the ratings you can.
Best of luck in your decision and feel free to ask questions, there are many professionals on this site that have a wealth of knowledge.