RJs have several advantages over props : they fly more per day, can go to longer ranges(though don't overexpand, you'll never make good money on a 2000NM route, 50 demand). But they drink more fuel than their prop couterparts. Beware, though, the drinking part has to be mitigated by speed. Let's compare a CRJ700 to an ATR72-500. The CRJ flies at 420 ktas, drinking 1460 kg per hour. This makes 3.47 kg per NM. The ATR72 will drink 600 kg per hour, at 275 ktas - that's 2.19 kg per NM. It's even better on very short flights, where take-off and landing have more impact than on longer flights.
So, depending wether the fuel costs 160$ per ton, or 1600$ the right choice won't be the same.
For those very long routes with small demand, RJs are better than props. Because you can fly 2 of them per day, without even flying by night. Anything smaller than a 737 needs at least 2 flights per day not to lose money, and preferably 3 flights per day, to make good
money. So for this ranges, props suffer much more from their lower speed. A CRJ100-ER can cover 2 daily flights on a 1000NM range, and make some money on it. But it' won't be impressive. Still, it makes a small profit, even counting the personal costs. Don't hope for ending up billionaire, though..... The advantage is that opposition on those lines is nearly unheard of, so you can just adjust prices once a year, and forget them the rest of the time.
Not recommanded for beginning a company. The shorter the route, the quicker the profit arrives. Once you are established, though, it can be a nice complement, if you have no better potential routes. And if you can afford a new fleet type.
And I repeat King Kong's great advice : limit your fleet types.