Agreed. The brake controller and rust would have been enough for me to walk away. I would have kept looking, but it appears that it's too late for that now. If he's already signed the papers and taken delivery, it's his truck. Being that it's a 2007 and the maintenance history is pretty unknown, I would do a full change of all the fluids. The engine oil was likely changed by the dealership, but ensure that was done. Otherwise, do a full change (three or four drains and fills) of the transmission fluid, a drain and fill of the rear diff VTM-4 fluid, a drain and fill of the front transfer case gear oil and a change on the power steering and brake fluid. I'd also change out the air filters for the engine and cabin, too. All of these are VERY simple to do on your own with only hand tools. You can save a pile of money if you DIY.
Being that you're quoting KM, I'd assume you're in Canada. That means the truck has seen "severe" conditions and the accelerated maintenance schedule should be followed. At 80,000 miles, you really need to check three main things: 1. the condition of the transmission fluid exchanger fittings on the bottom of the radiator. If these fail, you could have very big problems on your hands with the worst being a ruined transmission. 2. the proper torque and condition of the spark plugs. Whereas the issue seems to affect mostly 2006 models, the 2007 isn't immune to it. Basically, the spark plug in the #4 cylinder works its way loose and causes an issue with the head forming a crack. Very expensive fix. 3. know that the timing belt service is a good idea now. Being that the truck has likely been in very cold temperatures for an extended period of time, the timing belt could be getting towards the end of its life.
It's not too late for this truck by any means. We don't know how well the previous owner took care of it, but we can assume that it may not have been very well judging by the rust and the dent in the door. Dace, be prepared to put a little money into the truck. If you truly got it for $10k or less (USD), you got a steal anyways.