My friend started me a jade plant from hers. Can anyone tell me how long it taked for the trunk to look like a woody trunk? How old does it have to be to start pruning?

to NGA

There are two really good things about jade plants:

1. They will attain a nice size in just a couple years
2. They maintain a nice shape as they grow

It's like growing a natural bonsai. So to answer your questions, the trunk will start looking woody in less than 5 years. And, you don't need to prune until it reaches the size you want it to be.

To add to Daisy's apt comments, you will find the plant is rather malleable when it comes to shape.

I would recommend strong light (indoors that would be hours of daily sun) for good form and health. Outdoors you know you are giving good light when the leaf edges turn red. Avoid sharp increases in exposure at this early stage, instead make a few smaller changes so the plant doesn't get stressed out. In good light you never have to prune the natural bonsai form Daisy described. I'd say that's a worthy goal, especially because it's the least work.

Many of the jade plants you see in tiny bonsai pots (especially the ones with very fat, tree-like stems) were actually grown to some size in the ground (where they can become shrubs) and then cut and re-rooted for display. They are normally quite restricted in growth when the container size is limiting, which is something you can use to your advantage when space is limited. But if you want a large plant fast, provide a little extra space around the roots.