To start I would say that there are a lot of rewards to starting a horse. I start one or two horses each month, and I love working with the green ones. They are actually so much easier than trying to retrain a horse with bad habits. However, there will always be situations that you cannot predict, and it is very helpful to have an experienced trainer assist you in the process.
You definitely have the right idea with doing lots of groundwork. I believe that you can never do too much. Focus on getting respect and control on the ground, more than the pessoa rigging or side reins, as mentioned before, this is for more advanced training.
One more thing - for the first horse you get to start, be sure that he or she is quiet! A calm, willing, unflappable attitude will make your job so much easier to learn. If you decide to go for it, feel free to message me with questions! I love starting youngsters!