I don’t know where I got the idea that starting a sentence with “there are” or “there is” is bad, but I really hate it. Hate it. I will change it every time when I’m editing.
But why do I hate it? Am I just crazy? So I looked around, and sure enough, most people agree, starting a sentence that way is a bad idea. Not grammatically incorrect, but not the best form.
Grammar Girl calls it an “expletive sentence.” The reason it makes me uncomfortable is that it appears “there” is the subject and “are” is the verb, right? Wrong! It’s just extra crap in your sentence. “There are many pets in my house.” The verb is “are,” but the subject is “pets”: “Many pets are in my house,” though it would sound better if you wrote, “Many pets live in my house.” (Forms of “to be” are weak verbs in any sentence.)
Another irritating sentence structure is starting a sentence with “it”: “It is crazy to have so many cats.” Same problem — “it” is not the subject. “Cats” is: “So many cats in one house is just crazy.” It just sounds better. (Ooops! Started that sentence with “it.” Try again: That sentence just sounds better.
Which brings us to the real reason starting a sentence with “it” is bad: It’s vague. (Dang it, did it again!) What does “it” in this sentence refer to? Why should my readers have to even think about it? In high school, my grammar-Nazi English teacher would never allow us to use the word “it” in a sentence unless whatever “it” referred to was also in the sentence: “The dog is playing with its bone,” but not “It is playing with its bone.” Now, I’m not a grammar-Nazi, so I’ll still start sentences with “it,” but only if the last sentence had the real subject: “The dog was so cute. It was playing with its bone.”
So — don’t start a sentence with a dummy subject and a form of the verb “to be.” That sentence structure is weak. Find your real subject, and come up with a stronger, more active verb. Your sentence will be better. Even if no one would have cared before (except me).