I can’t speak to cycling, but I’d like to mention something that seems left field, but is actually very important. My dad has managed several pro sports teams, one of which was at the very top nationally for a decade (women’s hockey). One fundamental aspect are sponsorships, because cycling isn’t a sport with the same mass market appeal as, say, soccer. A lot of not-mass-market sports are run on a shoe string budget. So one of the hard parts is acquiring sponsorships and keeping sponsors happy.
Getting sponsorships and having experience interacting with sponsors is IMHO a very important skill for a pro athlete. What my dad was good at was getting buy-in from the employers of the players (who had to have a 9-5 job in addition to being a pro), so that they got fully paid time off for training, during the season, for training camps and during the championships. Not only might this provide some income for you and/or equipment (which, let’s face it, is quite expensive in cycling), but make you more valuable for the team. There are quite a few athletes who punch way above their weight when it comes to sponsorships as compared with their athletic performance. Anna Kournikova, for example, was IMHO more successful off the tennis court than on it, especially considering her relatively short career (which was cut short due to injuries). This is pure speculation on my part, but I reckon someone like Justin Williams has a better income than many pros who rode in this year’s Tour de France.