Who Gets Offered The Job
The first thing that shapes the job is who is getting offered the job. This shapes the job in a couple obvious ways - different characters have different interests and thus contacts from different fields - but also in a few less obvious ways. For example, one of my characters also does solo courier runs. A job being offered to him is likely going to be from someone who wants something couriered, knows him from his work as a courier runner, or has otherwise heard about him in that field. Another character is a bouncer at a night club. Most people going to them with work is probably going to involve protection or fighting of some sort. A third character likes bikes and bike racing. Mysteriously, most jobs their contacts have will probably involve the world of underground, or professional, bike racing.
Now, ultimately, these have little impact on the job itself. I could easily do a courier job that involved street racing and protection. But it comes into play a bit more with the next part.
Who Is Offering The Job
Most jobs in Shadowrun come from a guy named Mr. Johnson. Now, Johnson is a corporate stooge who meets up with Shadowrunners to conduct business. Payment for work that has to happen off the grid. However, Johnson isn't the only source for these jobs. In fact, almost everyone the PC knows could be the source for a job, and what relationship they have could be the difference between what needs to be offered in order to get the job accepted, and just what the payment may be on it.
Business vs. Personal
Who is offering the job is also where the fun comes in. A job offer from a friend is different from a Johnson. More to the point, a job offer from a friend is most often a call for help. This lets you add a bunch of little varieties to the adventure in question depending on whats going on.
Maybe the friend has the perfect plan for a big score but he can't get a crew. Word on the street though is that his good friend
Alternatively, maybe a friend reaches out for help. they need some help of the rough and tumble variety and have heard that their friend
The big thing to be careful with here is the potential to make waves. If a friend asks for help, and gets blown off, theyre probably not going to stay friendly too long. In fact, they could end up dead. Because of this you dont want to use the friends too often. If you keep making the PCs choose between friends and appropriate pay days they'll start to wonder why you are always trying to punish them. If you make PCs choose between two different friends, be prepared for the party to split.
That isn't to say that you cant do these things. Just be careful when you do do them and make it meaningful. If you are making the group have to choose between a friend and a payday have it be a rare occurence, and have the issue be somehting that could help out later or otherwise make the PCs feel good about the choice. If you are making them choose between friends make sure that the choice is there for more reason than just being a jerk to the players.
Most importantly, these choices shouldn't be "one shot burns the entire friendship" choices. There should be chances and means for the player to make amends, re-affirm the friendship and move on. If the player CONSTANTLY chooses the money over the friend...sure, maybe. However, if it only happens once it shouldn't be a deal breaker. After all, forgiving for small slights is kind of what friends do, no?