Corporate flying cannot be labeled in any particular way. It just depends on the place you manage to end up. The possible combinations are: high pay/easy flying, low pay/easy flying, high pay/difficult flying, low pay/difficult flying. On top of that, everyone's definition of the terms are totally subjective - one person's "difficult" is another person's "challenging or enriching". For instance - I personally would not like extensive international flying. I consider it difficult and worrisome and have tried to direct my career to avoid it, even though that is generally where the biggest money is. However, some people love that kind of flying.
You really just have to research the market, determine where you believe would be a good fit for you, and then apply. And apply, and apply, and apply, and apply, and apply. Apply until they get tired of answering the security buzzer and hire you just to shut you up.
It takes the persistance of a door to door salesman.
As to age, you're going to start at an entry level, time-building position like anybody else, such as night freight in a Baron or co-pilot on a King Air 90 at a charter company. Nobody is going to hire you right into a GV fresh out of flight school and instantly pay you the big money.
However, if you manage to get on with a corporate operator at a relatively young age, and show a great aptitude for all aspects of the job (and there are a TON of aspects to this job), you will move up, regardless of age. By the same token, if you manage to get the same job and have difficulty "getting it", you're going to stay in the right seat, or worse, for a long time.