You can haul using a stock dually (no upgrades) It's stupid,.....but you can do it. By reprogramming the computer,opening up the exhaust,and a few other nifty little tricks,you free up a TON more power and the end result is MUCH better fuel economy,and the side effect is more torque.
As far as a trailer,go with a wedge, I recommend a 53 footer with the flip dpwn extenders on each end. This allows you to haul 4 small cars,or 3 big ones. I prefer a tandem axle with dual wheels over the tri alxe set up due to tire wear on the front axle.
The 3 up one down trailers have you carrying a ton of tongue weight.
You can make great money hauling cars,but you have to learn the ropes. Everyone thinks centraldispatch.com is the way to go,...........Don't get me wrong. Alot of people make alot of money with them,but that flat rate per vehicle is not the best deal in town. I have contracts to haul out of several area auto auctions (much better $$$, paid per mile-per car) Then I use central for back hauls. I have 2 six car carriers,a 4 car (3 up/1 down), and a 4 car wedge. But I have all medium duty tractors,no duallys.
As far as start up money, Make sure you can operated for a minimum of 3-4 months with no income. Fuel,maintnance,insurance,driver pay,truck and equipment payments. It takes a while for the money to start rolling in. As with any business,..............you get out of it what you put into it. Hard work does pay off.
GOOD LUCK!!