Industry Structure

Gaining work as an illustrator can be difficult, but there are a few ways to break in. The most stable way you can earn money by illustrating is to work for something called a Design House, this is a company that employs illustrators, you would be paid in a salary rather than working for commission, though you would lose all rights to your work, and you wouldn't get personal recognition, you would become just another worker for a design house, most illustrators who used to work in a design house are very relieved to no longer work in one, it seems very constraining for illustrators.
Another way to work as an illustrator, would be freelance, pretty self explanatory, you work by commission, people come to you asking for work, you quote them for the work, then you get paid for that work, and you can reserve copyright, or you could sell that as well so that they now own that work entirely, this is probably the most common way illustrators work.
You can also work as a commercial illustrator, designing logos or advertisements. You could work as an on board illustrator for a magazine or other in print companies.

Mac vs PC

Ever since macs and pc's came about, they have been in competition to be the best hardware, and in a sense they have both became quite specialised in what they do. This will be focusing on their place in the industry though. Many people who have grown with pc's see macs a software used by pretentious photographers, and rich 14 year olds, but there is infact a reason that macs are the industry standard.
Macs were so much more advanced years ago, with better hardware, and stronger design software, at that time, pc came second. The industry adopted mac as the standard hardware to use, and formatted all industrial printers to it.
Though pc has now caught up, and some even say it has surpassed macs as a design tool, mac is still the standard, and changing now would only cause hassle, trouble, and confusion to printers in the industry. This is because pc and macs have different screens, what may look good on a pc would be over-saturated on a mac, which is what the printer would be using, this would lead to a whole run of print being over-saturated and ruined.
People who prefer pc like myself, just accept it is standard and get used to it.