I don't think it's a good idea to major in math. It will definitely limit your options for graduate school. If you're interested in economics, just major in economics. You can take whatever advanced math classes you want while working towards an economics degree. Alternatively, you could get double degrees in math and economics. My bachelor's degree was in physics, which required a lot of math classes. I flirted with the idea of getting a second degree in math, but was bored to death with some of the more arcane subjects like abstract algebra, topology, and geometry. If you really enjoy math, go ahead and major in it, but don't be surprised if it isn't what you expected.

The hardest math classes for me were calculus, differential equations, numerical methods, and linear algebra. If you can get past the first two years, it should be a breeze. Math is easy as hell compared to science majors like physics, chemistry, or electrical engineering.