You can't really go through Progressive directly, because most of their reps don't understand the expedite industry, and unless you know the exact coverage terms they won't have a clue what kind of policy to offer you. If you ever decide to get into the expedite industry call CIS
CIS – Commercial Insurance Solutions – Your Owner Operator Truck Insurance Pros! and let them handle it, there is a reason every expediter uses them. They know exactly what policy every expedite company requires and know the industry inside out.
As far as you own DOT number, wasn't trying to be a dick when I said that, but no single Sprinter driver should ever try to run under their own authority. First off you're gonna have to pay to join any of the load boards like Sylectus, Panther, Active Arrow, etc. and even then they are only going to award you loads if you work cheaper than anyone else (which is almost impossible with all the Russians invading the industry), or if the freight is going to a dead area nobody else wants to go. It literally takes years to build up trust with the brokers who award bids off those boards.
If you work for a smaller company that doesn't require you to label your truck and let's you work for more than one company you don't have to work full-time, you can literally call in when you are ready to take freight and they will look for loads for you, and when you want to be off you can call in again and take yourself off the board. They don't care if you take one load a month, you call the shots.
I'd strongly recommend against the 3500 Sprinter though, with the extra tires the wheelbase is too narrow to fit most standard skids, and most people that drive those have to build a false floor over top of the wheelbase to get standard skids in, and that reduces the height of the skid you can take. In fact I would skip Sprinter's all together and go with a full sized Promaster or Transit. There is nothing worse than breaking down in a Sprinter and desperately trying to find a shop that is qualified to work on them, only to find out that the repairs are insanely expensive due to the cost of Mercedes parts. You can literally put a new engine in a Promaster for the cost of some Sprinter repairs...