I have a few gardencenter / nursery seasons under my belt, abd I can tell you definately that homebuilt wagons are not wotrh the trouble.. they seem like a good idea, but they just aren't durable. For light weight and durable, go for plastic wagons and carts. The link I have included is just one source.. run a web search for garden carts or garden wagons and shop about.

Here is a link that might be useful: QCSupply wagons and carts

For $150 you can get steel 4-wheel carts from FarmTek or other greenhouse/nursery supply companies. I agree with virgo91967 that homemade ones won't be worth the trouble.

And, if choosing between 2-wheel and 4-wheel, I recommend the 4-wheel. At the nursery where I work, we have both, and I've found that the 2-wheelers tip forward when the load is uneven, leading to spills of plants. No reason for your customers to have to put up with that. :)

The 4-wheelers vary in quality, though. Some are clunky, heavy and ungainly. The ones I like most are rectangular (not squarish as some are) and have hollow rubber wheels that give with the bumps. The longer-rectangle carts seem easier to maneuver on turns, and are narrow enough to fit between tight rows of tables with breathing room to spare.

Keep the wheels oiled so they turn corners properly and don't squeal.

At my previous nursery they used kids' red wagons - the classic Radio Flyers bought wholesale in quantity. Will traverse most any terrain, they have reasonable lips to keep plants from spilling out and the kids love 'em. They either keep them busy pulling them or they like riding in them - either way they are occupied and NOT harrassing the plants or displays.

We also used a number of large flatbed carts. They were primarily intended to supplement the electric carts for the nursery staff to move up product to the sales floor, but they are also great for those customers buying a large quantity of bigger plants.

Around here you can get steel carts, the same thing as farmtek for $69.00. Don't waste your cash with Farmtek....
How do I know? The first threewe bought were from Farmtek...Then one day at Lowes...Saw the same dang cart...
And why pay shipping..

Thanks for that info, Mylu. Farmtek is fine if you don't have access to big box places and depend on mail order, but nowadays it's a rarity not to have a Lowes or Home Depot nearby. If they carry the same carts, then you can't beat that for convenience. I haven't seen them in my local stores, but I haven't actually looked for them there.

If you still want to make your carts, here is a suggestion I saw at a small perennial nursery. They had taken several old style baby buggies apart and converted them into carts and painted them a rainbow of colors whicj added to the fun atmosphere of the place.

We have picked up red wagons from the flea market for several years, the price is right. They are all a little bit different and a variety of sizes, but then again so are my customers. Works For Me----- Upnortdareh

Farmtek is good source if you have no alternative, but usually a sales club, like Sam's or Costco, will have them at discounted price. A few years ago I bought some for about $70 each. They had nice plastic trays, metal frames and large pnuematic tires.
Whatever you get try for the pnuematic tires. They handle uneven terrain and heavy loads with relative ease.

At the re-wholesaling yard (we have a retail garden center and a re-wholesale place for landscape contractors), we need the solidity of the professionally made nursery wagons. Toy wagons and revised baby buggies aren't sturdy enough or large enough for the quantities and sizes of shrubs and perennials that landscapers purchase in a typical visit.

Even at the retail garden center, we use sturdy carts (lighter than the ones we use at the re-wholesale nursery, but heavier than the average shopping cart) because of the tendency of parents to let their kids ride... Last thing we want is for a toy wagon full of toddlers and petunias to topple when it hits a bump.