In order to change these thesis statements, we must first understand what restricted and unrestricted thesis statements are. An unrestricted thesis statement is one that does not really narrow the scope of the paper much. By contrast, a restricted thesis statement narrows the scope of the paper. It clearly states what argument you are going to try to make in the paper.
One of the thesis statements in your question is “art can be a profitable hobby.” This is unrestricted because it does not really tell you what sort of art can end up being a profitable hobby. You could also say that it does not tell you how much profit you might make or how you might make it. So, we could rewrite this statement to fix these problems. For example, we might say “Art can be a profitable hobby because a person can make a few thousand dollars a year teaching others to paint.” This clearly shows what you are going to argue in your essay.
The other thesis statement in your question is “classical music is the basis for most rock music.” This is not very restricted because it does not say much about what kind of classical music rock is based on, how it managed to influenced rock music, and how when they are so far apart in time, and what aspects of classical music have affected rock music. We could rewrite this thesis to fix these problems if we know enough about the subject. For example, we might say “Classical music like that of Beethoven has influenced all successive types of Western music, including rock and roll. We can see its influence on rock in the scales and the chord progressions used by rock musicians.” Again, this makes the paper’s argument much clearer and narrower.
A restricted thesis is one that give a clear, definite opinion/topic which allows you to focus your paper on that specific idea.
For the first thesis you need to change the word can to is. The word "is" will show that art being a profitable hobby is the opinion you truly support and this allows your paper to be only focused on the benefits. A counter argument is needed because it allows people to see the other side, but your thesis should have your clear point of view. Next, you want to add evidence. Throughout your paper you generally have three reasons to back up you claim. You need to add those reasons with your thesis so that the audience will know what will be discussed and make them want to continue reading. "Art is a profitable hobby because it is unique, it is limited, and it is popular." This would be a more restricted thesis.
The second thesis has a clear opinion however it has no evidence. Just like the first it will need about three supports. You need to take the evidence you have gathered and work it into the sentence to show readers what you are arguing.