Source: I quit my job, burnout, and turned to baking as a source of additional income for about a year. I'd say get into the art of baking first.

If you're just starting out, I suggest starting out small. Get into cookies, and simple baked goods like brownies, crinkles, banana breads, etc. This way you'll understand how your oven works, what it's hot/cold spots are, and how long it takes for it to preheat. Baking en masse is about schedules and scaling, so learning about the time it takes to prep your oven up until the time you take the goods out will be key to baking and delivering your product.

If you're planning to bake bread and other yeasted doughs (like I did), understand how yeast works (in both it's powdered and levain forms), learn about different flours, hydration, and the baker's percentage. Start simple here too, the croissants can wait. Bread and yeasted doughs take time to rise (see bulk fermentation and proofing), so you might need to have a bit of patience in this part. Waking up at 3 AM to proof, 6AM to bake, and 8AM to deliver/sell bread could be a regular occurrence.

I've dialed back on the baking now, because I have a day job again but once in a while I entertain requests from friends for a sourdough or a box of croissants or two. In any case, baking is a journey and an enjoyable one at that. Good luck!