To start a good thesis, I'd suggest honing in on which parts of the story really speak to you. What message do you think the author is trying to deliver, and how can you present that as an effective road (or thought) map for your paper? Once you decide on these key ideas, the paper should begin to take shape. Just remember that the thesis should be a debatable yet defendable statement, and as you write it, try to link to specific key words or ideas that will become the body paragraphs of your essay.

Here are a couple of ideas that could work with the story (without knowing what speaks to you):

The narrator is responsible for Bartleby's death. In this paper, you could examine how the narrator has a greater moral obligation than he recognizes in making sure a fellow human is cared for. When the narrator abandons Bartleby to the new occupants of the building, he exhibits a lack of moral guidance in protecting this man.

Adhering to social norms is necessary in order to function in society. In this paper, you could examine how Bartleby fails to comply with what is expected of him. He doesn't provide any solid reasoning for his choices; he just follows his personal preferences. Your body paragraphs could follow how this break with the rules in his world ultimately leads to his death.

First person point of view allows Bartleby to remain a mystery, and Bartleby reflects a misunderstood segment of society. Although we know the thoughts of the narrator, who grows increasingly frustrated with Bartleby's antics, we don't really know why Bartleby acts the way he does. Why does he "prefer not to"? This could be extended to so many people in society who are misunderstood and are seen only from an outsider's point of view. If we as individuals don't make an effort to connect with those who walk outside the realms of normalcy in life, will they suffer the same fate as Bartleby? Do we all owe more to those who are different and who "prefer not to" do any number of socially accepted tasks or behaviors?

A thesis statement for "Bartleby the Scrivener, A Tale of Wall Street" depends on the idea you have about the story, just like any other thesis statement (which is short for hypothesis statement: something to assert, examine, and prove). The point of a thesis statement is to tell your reader what you want to talk about in your essay; and what you want to talk about depends on what ideas you have about the story: what question does it make you think of; what disagreement with the story do you think of; what insight into the meaning of the story do you think of; etc.

For "Bartleby," you might have an insight into why Melville mentions the dead letter office at the end of the story. You might have an idea about whether Turkey and Ginger Nut and Nippers are respectfully treated in their jobs, jobs which, by the way, were standard jobs for many, many people in that era. You might have an idea about why the lawyer couldn't be assertive with Bartleby.

Until you state your idea, guidance on a thesis statement is limited. A thesis in general is a short summary statement that explains what you think. A thesis for one of the ideas I mention might be something like this: "Melville mentions the dead letter office at the end of the story to show that Bartleby's troubles started before his work for the lawyer and that he really has more freedom at the lawyer's office than at the dead letter office."