Apart from a few odd instances - no alligators at all in the swamps one time, for instance - I've had no real issues with animal spawns. As such, the Trader role is my main money maker. Especially once you progressed a little and upgraded to the large wagon, it's $500 or $625 per trip.
I've not made nearly as much with the Collector stuff. Perhaps if I'd use that online map to complete collections, the income could rival that of the trading, but without that I've only managed to complete 2 collections so far, so I mainly sell off all the common duplicates. It's a nice bit of bonus income, but the trading earns money way faster.
I often combine the two, though - do some chill hunting to and from a collector search area, stuff like that. If I'd really focus on bringing in the high points carcasses, I could speed up the money making even more, but I see no real need to at the moment, not exactly strapped for cash.