Ah, yes. We English teachers have been debating this for years. English simply has no third-person singular pronoun. My opinion is that "they" is preferable to the clunky "he/she" when writing in generalities. For example: "A business owner might want to expand when they start earning at least $1 million a year." The subject is singular, but "they" is plural. To get around this, you'd have to replace they with he/she, change "start" to "starts" .... yuck! And the debate continues. At least in the southern states, they have the option of saying "y'all" (short for you all), but one can't really write that way.