Big Bri,
Here's my two cents for consideration. If this is what you want to do go for it. Just be persistent and be patient (and, of course, smart about how you go about it). The work is out there, you just gotta find it. Rarely will it find you. The more versatile you are, the greater your opportunities. It would serve you well to get a loader to complement the truck. I started with a F350 pickup, a little yanmar 2210D, and a dump trailer doing small jobs on the weekend and holidays. Now, I have a JD5403, tandem axle dump, and Case 450 loader. And, it is all side work. As I read the posts, I see that quite a few of the folks said that they parked or got rid of their dumptrucks and paid someone else to haul. Well, be the guy that does the hauling! After awhile, I hooked up with a guy who did tree work. He brought them down and I hauled away the brush and logs. When I moved to Northern, VA I started all over again. Small jobs on the weekend and holidays. Then I linked up with a landscaper pushing snow with my tractor and a buddy in the rollback business. He has a single axle rollback. I actually get charged less for my tandem axle dump than he does for his boxes. So, if he has a lot of heavy debris, I will haul it to the dump. Unless, you are going to haul strictly sand gravel and dirt, I would get an F750 (or equivalent for you non-Ford types) with a landscape body rather than a construction body. Gives you more versatility. Brush,mulch, and general debris doesn't weigh much but it fill you up quickly. And, you will come across a lot of brush and debris jobs in between sand, gravel, and dirt loads. Otherwise, I wouldn't recommend anything larger more than a tandem or tri-axle dump. In addition to the dump trailer I pull behind my pickup, I have a '74 Diamond Reo with a 14' bed. I would prefer a 16' bed, but it was a good price. My mistake, I was over anxious and it was in lot worse shape than I originally thought. It runs and operates great, but there are a lot of little things nickle and diming me to get it right. There is no way to get around fuel. Insurance and how you tag it will be a big factor. I pay $275 a month with Progressive. And, I have non-apportioned tags. So, I can't run out of the state of VA with the dump truck. If you are nowhere near the state line, then it shouldn't be an issue for you. Again, network, be versatile, be persistent, and have a little patience! And, I think you will find that you can make it.
Hawk