When building nearly any business, developing the groundwork and foundation are the hardest parts and also the lowest paid, as there is no income coming in from the business yet.
This is one of the most important things that most people don't realize. I've started multiple businesses over the years and the first 6-18 months are the worst, then things start to get better but not great. This is the point so many give up. They compare the effort to the rewards and say they are 2 years in and it's just not enough income.
Most quit just before they achieve success.
this is also why those who succeed generally do better than average as the average quit early.