Sculpture varies in accessibility depending on the type you choose. For example, Ceramics has a high barrier to entry (cost and space), but 3D modeling has lots of free classes and can be done on most computers. On the other hand, there are a lot more instructional, in person classes for ceramics then 3D modeling. Accessibility just depends on type and the resources you have.
There is no words to describe how important ventilation, masks, gloves, and other safety tips are to sculpture. If you plan on doing sculpture for a long time, then you need to put safety first. Even 3D modeling, which is only on a computer, requires "get up" breaks for safety.
This depends on commitment, popularity, and use of a medium. Ceramics can be highly lucrative if replicated with molds; High Polymer Clay has a big presence on Etsy for key chains; and 3D modeling can be applied to carriers. Anything can make money as long as you know how to market your work.
All art has a learning curve, but the joy of sculpture also comes from trial and error. So however steep the curve is for some people, and no matter how frustrating it is, struggling means you are learning.
The Easiest way to learn sculpture is to watch videos and take classes. The latter requires money, but you do get what you pay for in the way of hands on teaching. To learn, however, you also need to just create. Practice is when you learn the most things