For entry level multi piston/caravan:
###### operators - same as first year airlines 18-24K.
Average operators - 28-35K first year.
Good operators on a good run (takes a bit of luck in this market) - 36-48K first year.
Second year average probably about 40, all depending on what you end up doing. Turnover used to be high enough that a year worth of seniority could move you where you wanted to be.
3-5 year airline pay similar to freight dog pay. Cargo pay for the entry level work usually stays stagnant.
Good overview by spilot. Pays better more quickly than regionals, lags at the top end (if you're still talking 135/feeders). At my company (edit: I should add, mine is not exactly entry level...usually a second-stage 135 job, from what I can tell), you might make $60-65k on a good year if you fly charter/on-demand and bust your hump. Maybe $45-50k if you fly a regular check run. This goes up very slowly after your first couple of years. I think long-term Fedex feeder guys in the ATRs can make ~70k with some pretty easy flying and schedules (home every night, etc), but that's 10 years down the line at least. The flying is (imho) more fun, but it's harder (not impossible) to make the jump to "heavy iron" from a 135 background than from an airline background. Even the big cargo companies (in my highly unscientific survey) are mostly crewed by former pax guys.
That said, I wouldn't change a thing. Freight is great!