Bill,
whats your suggestion if I have to go buy 'soil' to fill this thing? Just get top soil from someone and have it delivered or buy some in the bags from one of the big box store type stuff?
Since I have buy something anyway, could I get away with buying potting mix? Except it might be more expensive.
Aaron,
Potting mix will set you back a ton, especially if you build up the beds significantly. Some places will sell you "top soil", but you should think of it as fill dirt... I've never seen any actual top soil for sale... I've seen a lot of dirt amended with sawdust and sand, though. The stuff is cheap (as it should be), but the delivery charges will hurt.
If there's nowhere on your land where you can get dirt, here's your best option: buy a pickup load of what they call soil. It should be a third to a half of your total need. Dump it near, but not in, the built beds. Then see if your county has mulch. In most places, you can back up your pickup right up to the mulch pile, and take all you want for free. It's not the most pleasant work in the world, but it's not too bad. Bring a digging fork as well as a shovel. Trust me on that one...
Dump it near, but not in, the beds. Then go to one of the big box stores, buy some peat moss, and some high nitrogen fertilizer. You'll need a few bags. The numbers on the bags will tell you what to buy. Look for something like 10-2-2. You want that first number high, because you're going to need the nitrogen.
If you lived east of the mississippi, my recommendation would be different... traditionally forested areas have a more acid soil, and you'd need lime, which would mess with the nitrogen.
So, once you have the beds where you want them, with either mesh or landscape fabric on top of the original soil level, start shoveling!
I usually make a 2' x 2' screen out of hardware cloth and 2x4s. this breaks up clumps, gets the rocks out, and helps with mixing. If you use a screen, you don't have to get in there and mix, and you don't want to ever, ever, stand on the soil in the beds. That would compact it, and you'd lose a big advantage. A couple shovelfuls of dirt, a couple of mulch, one of peaty moss, a small handful of fertilizer. Repeat. It goes pretty fast. When you get to the top of the bed, flatten it out so its level. Then water it in, with LOTS of water. You want to get the whole thing soaking. You'll lose a fair amount of volume... but that's ok... you want the top 3 or 4 inches to be pure mulch. That will mean no weeds, and you'll get past most of the watering problems. East of the mississippi, I've had raised beds I never needed to water, precisely because I used several inches of mulch. Your mileage may vary...
If you do this as soon as the ground starts to thaw (or even before), they'll be ready to plant by the time the danger of frost is past. The beds will need a few weeks to settle in, so don't wait till spring...
Oh, and there'll be a sign at the mulch place saying "only use this for ornamentals." That's because they have no control over what goes in to the pile. I never worry about it, but I make sure the beds have a few weeks to settle, with lots of water, so most of the yuck has time and cause to leach out. If you're a theory driven organic gardener, you can replace the mulch with homemade compost and more peat.
I know it all sounds complicated, but it's really easy...
One final caveat: no-one ever believes me when I say this... but even if you keep your construction costs low, it's actually cheaper to buy veggies at the store. Think of it in terms of woodworking: we don't build furniture to save money, we can't actually compete with the stores. We do it because we enjoy it, and because we can make exactly what we want. The same is true for vegetable gardening... we can grow varieties we can't find in the store, and we can be sure of how they're grown, and it's fun and challenging...
Thanks,
Bill