because Gmail has more space capacity than yahoo. Plus you will also have different functionality if you own a Gmail account, like on youtube, blogger, drive, maps, etc.
having a business doesn't require any degree, as long as you love what you do and you have interest in what you are doing, i think everything will goes out smoothly.
to start your online business, first is choose a niche that is within your interest. then get a website and domain of your own. build your list and offer your product or service to them
for me either you decided to invest your business online or offline, mobile business would be a great choice because most of the people right now own one or more than two mobile gadget.