My first post here, but this is an easy question. If the unit has been sitting for years without being prepared for storage, then the carb has long since gummed up. Modern fuels don't bode well sitting in carbs with tiny jet orifices, like in ATV's or multi-carb motorcycles. 6 months is all it takes and the carb can clog. Plan on a complete carb disassembly, cleaning and reassembly. I can't tell you how many times we, at Roseville Yamaha, got units in that wouldn't idle, or idled but wouldn't accelerate after sitting for a couple of seasons. There was good jobs from that, but you had to be thorough or you'd have to do the job again because it if you missed the smallest detail (clogged jet or port) the bike wouldn't run right. I tell you this only because if you do the rebuild yourself, be sure you don't take shortcuts. A jet can look fine to the naked eye, and pass fuel, but still be partially clogged, requiring physical cleaning with a soft cleaning device (i.e. toothpick vs. file).
With a no start condition on a unit sitting that long, there's a good chance the carb's idle and high speed circuits are both plugged.
Figure on a new battery. Shop online, you'll save 40-50%. Plugs are cheap, buy one. Change the oil and filter now, and the oil again after the unit has run a few hours. I wouldn't worry about the brakes until the unit can make itself roll. Then make sure the brakes work before you make it roll too fast.