There are two meanings of the question "how often do you ___?" The first is the literal meaning. How many times per month, per year, etc. does something happen? For example:
A: How often do you work out?
B: Probably two or three times a week.
The other meaning is a rhetorical meaning. You ask "how often do you ___?" to express that something doesn't happen very much. Here's an example of that use:
Wow, your son actually keeps his room clean without you asking? How often do you hear about that?
In the example at top, the speaker is saying that people don't often get the chance to move to another country. That's why the speaker is going to take the job.