In my case there was already a tow bar on board and I bought a Brake Buddy which I installed by myself, making necessary brackets for the breakaway switch, plus installing a secondary cigarette lighter on a new panel. So my cost was only labor spread out over several days.
On the money issue, I got mine on fleaBay and saved $700 over retail price and its like new. I did have to buy a breakaway switch which was missing, and BB sent me a power cable for the remote control gratis.
MOTHER SHIP Winnebago View 24H (2007 Dodge Sprinter 3500 Chassis, 2008 Body)3.0 L M-B Diesel V6 bought used with 24K miles. Toad: ROCKY the Flying Squirrel.