You know ChickiesMomma, that work in a greenhouse is awesome! I have so much to say!
I worked in a greenhouse nursery for a good number of years. I got my job by making an offer, and just by being in there doing the offer, and when things needed to be done, just assisting and doing them, even raking leaves and cleaning. Inside a month I was working there. My offer was to grow and hybridize tomato heirlooms for them to sell, but just leave me the best plants for seed, and any that didn't sell would become salsa the owner's daughter in law, a friend, wanted to make.
My suggestion to make sure you get that greenhouse job is BE THERE doing stuff, uppotting, propagating, making sure you know the heating and fan systems real good. Be behind shelves cleaning, bringing in the bags of soil mix, helping with any shipments that arrive. Be there before it opens. Next thing you know, they're giving you the key so you don't have to wait...next thing you know "just to make it official fill out the application form and by the way can you be here 40 hours a week?"
About starting your own business doing it, think about the business of propagating plants, just the raw numbers first: Take one Dahlia for a simple example. In one year, it can go from being one seed from a packet of 20 seeds of a special mixed variety. By October it has made 3 to 8 tubers! Not only that, but during the season you might have started 5 cuttings from it, that make small tubers you don't yet want to divide. So, next spring, from one seed you have something like 10 plants. Each of those make 10 plants by the following spring. That's 100 plants!
Well, as you can see, even before you start your own nursery of any kind, now is the time to begin getting your future little moneymakers going!
Let's say you can start Crabapple trees from seed. They breed "kindasorta true", and more or less so depending on variety. One year old trees are little 5 incher seedlings worth maybe 3 bucks each in 4 inch pots, (whatyever it is these days), but let them grow another year, now in gallon pots they are 10 dollar trees. Let those puppies grow another year and they are 25 dollar trees in 5 gallon pots. Getting the idea? I don't think stock in xerox in 1935 ever grew that fast!
Perennials that are dividable, shrubs that make growable seed or good cuttings, same with trees; these things make a great pre nursery start!
If you can do the same with your pond plants, even better, because that's what you love.