I made myself an 'adult hoop.' I haven't done it consistently for exercise. I just grab it from time to time and have fun. I'd like to work with it more, when the weather permits, and learn some fun moves. You can't target zones to lose weight, but you definitely can tone up your stomach/core muscles by hooping. I can really feel it working things.
I have a 'kid's hula hoop' as well. I have many friends that have tried the kid's then the adult and the difference is amazing. They go from it instantly falling to being able to at least hoop a little with no practice.
The only cost is buying materials to make your own hoop, or to buy one from online. You can find free instructional videos online that teach moves/tricks if you want to go beyond just going around your waist. There are a few out there that can be bought, but I haven't found the need to yet.
The hoops do weight a few lbs. I have no clue how much, but when I first start I do get some small bruises on my waist/hips. Then my body gets used to it. This is a great tutorial that I used for making your own hoop.
It's a great project to grab a friend or two and make them together. I love being able to decorate my hoop to match my personality.
If anyone has questions feel free to ask.