In the latest Make magazine, they mention two 3D design programs available on the Internet, Tinkercad and 3dTin, both offered at the now very popular price of free. After I wrote about Autodesk Inventor Fusion a few weeks ago, also free for a limited time, I couldn't help but think, some of this free software could be very expensive and you should compare what "free" costs before you start your next 3D project.
None of these software programs will do anything before you learn how to use them and some are quite basic and easy to learn. Spend a few hours playing around with the simple programs and you'll be turning out designs that are as good as any examples shown on their websites. If that's what you want to do, fine, but I used the word "spend" on purpose. Spend enough time to push the software to its limits and the results will still be very limited.
Now compare programs like Tinkercad and 3dtin, or many other similar programs, with Autodesk, difficult, really, because the programs aren't remotely comparable, however, learning Autodesk Inventor Fusion is an "investment" of time, the learning curve is steep and it will take long hours for many months to become comfortable with it and before you can turn out professional level work, even more time will be required, but that's the difference. The time involved pushing this software to its limits will enable you to produce high quality designs and you'll have a skillset many companies and organizations recognize, the software is an industry standard. Not only have you learned a skill that can be directly useful to you for creating designs for projects of your own, you've mastered a skill that others hold in high regard as well. Much more time is involved than what's required for the light duty software, but the payback in new valuable skills is immensely greater.
Let me be clear, something like Tinkercad is useful for simple projects and not everyone needs to be a CAD pro, you certainly don't need to master a high end program like Autodesk Inventor to perform simple 3D design functions, but it's important not to confuse the two. The simpler programs must be almost immediately useful returning value for the time spent or the scales quickly begin to tilt away from simplicity and towards real capabilities.
What is your time worth? What do you want it to be worth? How many hours do you want to spend before expecting valuable skills in return? Learn and practice the hard stuff and you'll get the greatest return for the time you invest. Don't let free fool you. "Free" software that wastes valuable time can be very expensive.