What all do you need in order to buy a 16'-18' box truck and use it to create revenue?

First, you need to decide how you're going to use it, and there are quite a few ways.

Then you need to buy the truck and insure it according to DOT's requirements for what you're using it for.

You next need interstate authority from DOT--even if you're only going to use it in one city. What DOT considers "interstate" work is weird: if the product you carry is made in another state, or it'll wind up in another state, you are an interstate carrier.

You will then need intrastate authority for all the states you are going to operate in, which will require you to hire an agent in each state.

Next, get an International Fuel Tax Authority registration. They'll send you stickers. You'll have to file fuel tax reports on a regular basis--how regular depends on who you are and how much you drive.

There are four states you have to pay road-use tax to separately from your IFTA road tax filings: Kentucky, New Mexico, Oregon and New York. If you're going to operate in any of those states you'll need to register and file reports on a regular basis.

Next, your driver's license. You will almost certainly need a Class B CDL unless the truck weighs over 26,001 pounds--no, I don't know what the extra pound is for--and then you'll need a Class A CDL. If your truck has air brakes you need an endorsement for them. If you're hauling hazardous materials you need an endorsement for that. And you'll need to take a DOT physical.

As you can see, this may not be the business you want to get into.