A lot of stocks doubled last year. Some of them were so low a year ago that they are still fetching single-digit stock prices. Nu (NU -1.78%) and Opendoor Technologies (OPEN -6.98%) are two of those low-priced winners of 2023.Most of last year's big gainers aren't likely to repeat the feat in 2024, but I think that Nu and Opendoor have the potential to double again this year. Let's take a closer look.1. NuIt's OK if you're not familiar with Nubank or its parent company, Nu Holdings. Unless you happen to be ...