Please check this paragraph, Sir

Sanjay, most of my comments today will be about style – the “art” of writing” – and less about grammar. In your first sentence, you have a choice of how to tell us about John. You can use a relative pronoun clause or an appositive. I’ll show you the difference:

John, who was an intelligent young boy, had no father.
John, an intelligent young boy, had no father.

With your second sentence, you also have several choices involving the verb form.

His mother had to work …
His mother worked …

The first, “had to work,” suggests the mother was compelled or forced to work. The second only conveys the fact that the mother worked. If you want to emphasize the mother’s need to work, you may wish to link the reason “to bring her son up” more closely with the result. You can do this by making the reason an introductory clause.

To bring her son up, the mother had to work …

The second sentence also offers opportunities to make the story more interesting, to spice it up. Here are some examples:

John’s mother had to toil …
To raise her son, John’s mother had to labor …

Your second sentence also suffers from “prepositional sprawl. You can streamline the sentence somewhat:

as a security guard in the basement of a New York Avenue office

Here is one version of the second sentence. I have indicated places <?> where you might add an adjective to make the story more descriptive. Pick your own words. Don’t overdo it.

To raise her <?> son, John’s mother had to labor as a security guard in the <?> basement of a <?> New York Avenue office.
To raise her only son, John’s mother had to labor as a security guard in the dingy basement of a soaring New York Avenue office.

I'll come back and comment on the rest of the story in another answer.