yes you can use a 3s lipo with a brushed setup. just get a good ESC. the tekin fxr i have can handle 3s and there is other brands that can do that and more.
one thing i have learned a hard lesson from is you get what you pay for. you can hurry up and get things from super crappy no name brands because there cheap and have them burn up in minutes to days or a few weeks or you can save some cash for something that is dependable with good support that will last longer. for example a lot of good motors are rebuildable so when the brushes wear down it will be easy on the wallet to get back out on the trails.