Good timing because I just did this last weekend.
The frame is 1" x 1" x 0.25" angle iron and 2 inch casters from amazon. I think the steel was around $20 and the casters were around $15 total.
I don't have a reliable way to cut 45 degree miters, so I notched the angle to make the square sides. That worked fine. The wheel mounts are just flipped angle with 1/2x13 nuts welded to them. If I find a good permanent spot for the cabinet, I might replace the casters with leveling feet.
The drawers are not in, but I don't have any real concerns with tipping. Even with some weight on top, I think it would be fine with a little caution. I did use 2" wheels with that in mind, however.
Concrete in the space below the drawers is interesting and I might weld in a couple straps to support a cheap paver,
In any case, I'm happy with its properties so far and I think it will be a useful addition.