How about buying bags of potting mix ? I don't put my pot plants in soil, always potting mix. Just the ordinary old bag from the nursery. I make sure its the Australian standard mix, though.

Good luck with your enterprise.

Popi

Just thinking out loud.
Try to have a second market where you can sell CHEEP if you have to, just to move your product. The man who runs the local stand about a mile away from me has a saying that I hear him say often "Don't fall in love with it" meaning, you have one price in mind, your target price and maybe you will get that. If not, don't fall in love with the produce or the price. Move it, even if you have to drop your price.
Do be careful about the fire ants though. That will get you a bad reputation very quickly. Use what ever controls are needed.
Start small. It's a great feeling to sell out! You can always grow and sell more next year.
Grow what works for you. Most nurserymen and women have certain things that the just grow better for what ever reason. Grow what you grow well.
Don't try to many things all at once. Again start small, not only with quantity, but with variety also.
Talk to your customers and listen. What are they asking for? what is there real reaction to your product?
Don't count your chickens before they hatch. Don't promise goods before you have them. Don't promise money you haven't got, hoping you will sell something.
Grow pretty. People like pretty. Their faces should light up when they see your product. They will remember that long after the pain of the price tag has been forgotten.
And speaking of price tag. Don't be afraid to start your prices at premium. One of the biggest mistakes I made starting out was trying to be too cheep. Worked Worked Worked like crazzy only to make $1.00 per tree. You can always let them "talk you down" so they feel they get a really great deal.
Enjoy! life is short, may as well have a good time doing it.

Where I live there is a distinct season when money can be made selling plants - Spring. Once summer gets hot and humid people don't want to spend too much time in their gardens so plant sales drop off. And even though there is a lot of information telling folks to plant stuff in the fall very few people buy plants in that season. The biggest problem is that EVERYONE else is selling plants in the spring. Every gas station, grocery store, church group, scout club, you name it - bedding plants are available dirt cheap from just about anywhere. It is very hard to grab the customers attention during the spring. You have to grow really special plants and market them well. But things might be different where you live.

This year I sold plants at a small farmers market about an hour away from my house. I loved the market and plan on participating next year. But sales were weak. I never sold out of anything. There were a few days where I made over a hundred dollars but by mid summer I was lucky to make $50. You have to go where there are people wanting to shop and that can be hard. There is a much larger farmers market nearer to my house but it is full of plant vendors in the spring and the competition is harsh (besides the fact that I would have to get there at 4 in the morning!).

We are currently growing plants that are unusual and are planning to market them in a niche setting.I also think of our plants as stock we start with little and grow them into
large salable plants. Find what you do and do it well.