no "massive" amount of money to make, even if you do own your own shop. those of us who do it, don't really do it only for the money... the VAST majority of shop owners (the good ones atleast) do it for the love of the sport.
but yea, like it has already been stated, you can start out with MECP cert, and then look for work at a local shop... your first job at a shop WILL not be glamorous. you will most likely be doing mostly clean up, coffee runs (beer if the shop is really cool), and helping out around the shop. but, this will be the most important time of your career. Use this time to soak up as much info as you can... really is the best way to learn. After a while, the owner (depending on his confidence in you) will begin to give you installs here and there, and depending on how well you do, you should progress on the complexity of the installs from there. after working at a shop for a while, you can start thinking about opening up your own shop.... but it's not easy, and DO NOT expect a profit for atleast the first few years.
and remember, this industry can be very cut throat, so just because you do good work, that doesnt mean that your shop will succeed... its a very hard business model to make succeed.