Sales & Relationships division at investment management firm?

I presume you mean the wholesalers?

Basically they go out and pitch financial advisors on using the firm's mutual funds/ETFs/closed-end funds, etc. Most start as internal wholesalers on the desk calling FAs and either selling directly or trying to set up meetings for their external.  The standard career progression is to become an external.  As an external you normally live in territory and meet with FAs full time.  It's very much an eat what you kill career, but successful externals can end up pulling down a million a year for 50-60 hours a week of mostly golf and client dinners.  The base is normally super low though in the mid 5 figures, and it's all incentive/commission.  I'd guess the average income for an external at a major firm is $300-500k, meanwhile internals make around $75-100k base with a small bonus unless their external is happy enough with them to kick something their way out of their own pocket.

There are other variations on this theme like working in the various institutional spaces like private bank and retirement plans all the way up to pensions and sovereign wealth funds. (I'm working with a sovereign fund right now, it's pretty fun, but it kills me they really don't get the time zone difference or US holidays.  Seriously, who schedules a meeting for 3AM NY time on a Thursday?)  With the wholesaling route, the short answer is no, it is rare to move elsewhere unless you utilize your connections to pull a straight-up lateral at your firm, and possibly even take a pay hit.  I know a couple smart kids who did just that to move off the internal desk and into my group.

Of course I could be completely wrong here.  The title is pretty vague, it could involve home office relations, which is a completely different animal.