Can you be trucking at 18?

Yes, but with severe limitations. If you're looking at driving something like a Class 6 or 7 single axle truck within your home state, you might be able to find a job doing that. If you're looking to get into tractor-trailers, your chances aren't looking so great. To be able to haul commerce interstate, and/or get a hazmat endorsement, you must be 21 years of age. At 18, you could only operate a commercial vehicle within your home state - problem is, local companies don't have the means to train new drivers - they require experience. The only companies which really train new drivers are your major entry level interstate carriers such as Stevens Transport, Swift Transportation, Schneider National, etc. Most of them won't hire anyone under 23, and, even those that do still require you to be 21.