I have been a courier in the Baltimore/DC/Northern VA for fourteen years and it has been pretty lucrative for me. For years I drove Crown Vic ex-police vehicles picked up at auction by my bother-in-law (a major taxi owner in Baltimore). While these vehicles were ultra reliable you were somewhat limited on the size of things you could carry. I bought a Prius from him about 2 years ago and have been really happy with it, especially spending 1/3 what I used to spend on gas. In this area, $150-$175 a day is pretty easy to make. Some weeks are good, some not so hot. December and January were good for me. Both months I drove over 10k miles each and in January alone I grossed over $7000 (unusual). The company I contract for does more long runs than most local couriers, we go up and down the east coast (upstate/western NY to North Carolina). Every now and then we go to MIA. We carry a lot of human organs and also have a contract with an aircraft parts manufacturer. When a plane is on the ground and can't wait for the next flight out for a part, we drive them. We go to Buffalo a lot, especially during the winter.
You really have to check out the courier companies you may want to work for too. There are a lot of crooked owners out there as I guess there is in any transportation businesses. The company I work with now pays a 65/35 split which is something rarely seen. You pay for your own gas of course and he pays most tolls to the delivery out of the DC area which can really add up going to JFK a few times a week.
I just bought a '15 Promaster 2500 diesel high roof to see about getting into otr but not real crazy about being on the road weeks at a time and sitting waiting for loads days at a time. I guess that's why I joined this site, to learn about van expediting and different companies. Been getting a lot of good info here reading quite a bit.