But on the other hand, a spinning wheel is just a wheel, attached by a drive belt to a shaft that turns the spindle. And I had a wheel: an old bike wheel. Which I could easily turn into a spinning wheel:
This wheel is a "walking wheel," named that because when you spin on it, you stand next to it and spin the wheel with one hand, doing a kind of back-and-forth dance as you spin and wind up the yarn with the other hand. Youtube has some great videos of people using this kind of wheel.
To make the wheel, I used an old bike wheel, some lumber that I found on the beach after a storm, a Tinker Toy hub, two old knitting needles, and some clothesline. All of these were things we had around the house. Cost to make the wheel: $0.00
To make the wheel, I made a frame with the lumber. There are two hubs, one for the bike wheel and one for the spindle. Here is a closeup of the spindle hub. The rope goes around the bike wheel and around the Tinker Toy. When the bike turns, so does the Tinker Toy, and so does the knitting needle inside the Tinker Toy. When you spin, you wind your new yarn around the pointed end of the knitting needle where it sticks out from the frame. The needle is pretty short for this, so I may replace it with a longer dowel that I scavenged from a broken window shade.
Here's the other hub, where the bike wheel is attached to two other posts. I drilled holes in the posts and ran a metal knitting needle through them. The bike wheel spins on this knitting needle axis.
Now all I need is some wool...