The introduction and conclusion should contain a thesis statement that clearly and concisely summarizes your essay.
A thesis statement is supposed to clearly indicate what you are writing to prove in your essay. Since your essay is a cause and effect essay on homelessness, you must be arguing that the three particular causes were responsible for homelessness. How can you generalize them to one theme? For example, let’s say they were all related to the economy. In that case, your thesis would be that the bad economy caused the homelessness.
The economic recession has caused an increase in homelessness in America.
If this is your thesis, you can then build an essay around it where you describe how the aspects of the economic slowdown that you describe contributed to the problem. For example, you could describe how the drastic drop in home values caused an increase in home foreclosures. As a result, more people were forced out on the streets and unable to afford a new home, especially if they also lost a job.
In your introduction and conclusion, you want to make your case. The introduction introduces your argument to the reader in the form of a hook and thesis, and previews your points. The conclusion restates your thesis and summarizes your points, reminding the reader of your argument and why you made it convincingly.