Not really the place for this as it's not even writing really, but I can tell you, since it's my former field.
You get hired and work at the bottom. You get a flat pay and you work for as many hours as are needed. The pay at the start isn't great. I have no idea what current wages are, so I use this as a random figure. You land the job and you get 25K a year. In theory you're working a 40 hour week, but if you are needed, and as a bottom-rung grunt, you are ALWAYS needed, you can easily find you are working a 60 or 80 hour week for that same pay.
As you progress in your career (and you won't progress through a company, you have to leave the company to get a promotion - then you might well leave that job to come back to the FIRST employer to get another promotion) the pay gets better and you can charge an hourly fee and get what you are worth.
If you are good enough, you should find someone willing to hire you, but it's the realities of the job at the entry level that REALLY make things difficult. Can you afford to take that kinda pay for those kinda hours? If you have a family, do you REALLY wanna be working those hours?
It's a hard business to work in. It is VERY subjective even when you know ALL the rules of design and advertising. It has fashions that come and go. And you often have to deal with people who THINK they know exactly what you should do and don't like to shown the error of their ways... even when that is to their own benefit.
But it's a lot of fun, exciting and if you can stand the pressure (actually, you need to get a kick out of the pressure) a very cool job.
