Florida is totally different from Iowa so try and get local advice.
But here goes a very simple over view.
First you need land that has both Electric and Water. In your case Green Houses My case SHADY trees or Shady houses.
I started by first having a holding yard for planned installs. If I needed 20 of the same 3 gallon plants, I purchased 25 or 30 so I had replacement if some went bad. Slowly I accumulated plants over the years until I reached the point of actually having some inventory.
I found it was better for me to purchase certain plants and Propagate only those easier plants. There are in fact short term plants that have a lower profit margin but turn over quickly to create CASH FLOW. Next are the Medium fast growers with a higher profit margin but maybe a years turn around time. Of course Trees become high dollar long term projects that might be better considered as retirement planning. Proper space planning is important so Trees that grow big will have room when mature yet other plants can be grown between them especially went young.
Growing Nurseries work on a high volume low profit. It takes a huge investment and high risk to be successful. I took a one year course at the local Voc Tec on Nursery Management before trying to start a nursery.
The down side is Mother Nature can wipe you out with a multitude of Natural occurrences. Hurricane Charlie was my down fall just as I was in the process of going full retail. BTW Crop Insurance is available but at a price. Looking back, I couldn't afford the insurance and still of made a profit. Of course I am out of the Nursery Business now because of Hurricane Charlie. Plus add in the Big Box stores That sell plants cheap and Guarantee them. That is your biggest competitor in the Nursery business. People will come to you for advice and go to home cheapo to buy the plants because of the Guarantee we can't afford to give.
The real profit in having a retail Nursery are the UP SELLS. Installs and Maintenance are where the money is. By having a retail Nursery you raise above the Average Yard Boy and can get more work at better prices. I have both Pesticide and Irrigation licenses which really put me a leg up on the up sells.
it is one thing to do a off label applications. It is total stupidity to post it on the world wide web and expect people to approve.
You can lead a Donkey to water but you can't make the Jackass Drink