Depending on where you live, rocks can usually be had for free.
Just have to go pick them up.
(I can't dig an inch without hitting a rock here in Arkansas)

I've used 10' lengths of aluminum, 3" or 4" wide, from the roofing dept of HD, as well as wider aluminum roof flashing that comes in rolls (can't recall what the narrower stuff is called, edging maybe???).

However, its edges are *sharp*:
Wear substantial gloves when you handle it.

I feel okay using it because there are no children in my household & I only use it in the back yard.

I used the wide stuff along a wood fence to protect the wood from contact with damp garden soil, & the lengths to make the sides & ends of the beds.
It bends easily, so you can use it for sides/ends that are less than 10'.

The 10' sections were $2.99 each.

Best luck!

thanks for the flashing idea..my son-in law is in construction and i know he has some at a jobsite that they just throw away...i'm afraid the the rocks will take up to much room...

One thing I used last summer was old cedar shingles. Don't know the cost if you were to buy them but they look great. They were two feet long, so I cut them with a jigsaw down to 1.5 feet and buried half with the other half above ground. Created a nice edge for a raised garden.

I've made wooden raised beds out of free pallets. I just take apart the pallets and use the 2x4s. This might work for you. it takes a bit of effort to pull out all the nails, but it's free and it looks nice once it's finished.

Tiffy, I'm so glad the cedar shingles worked well and look good. I just got a bunch from someone on Freecycle and that's what I am planning to do with them.

Great minds, huh? :)