The high-growth fintech company has a bright future ahead.Nu Holdings (NU 0.83%), one of Latin America's fastest-growing fintech companies, has seen its stock rally more than 50% over the past 12 months. It impressed the market with its robust growth in customers, revenue, and earnings.Should you buy Nu's stock before it posts its fourth-quarter earnings report in February? Let's review its business model, growth rates, and valuations to determine the answer. How rapidly is Nu growing?Nu's NuBank is the lar ...