Source: answer explanation for Housing Market SC question from my CATs

When comparing clauses (i.e., a phrase containing a subject and a verb), we must use "as" instead of "like."
For example,
"She sings like her mother"
and
"She sings as her mother does"
are both correct, but
"She sings like her mother does"
is not.

I agree that the second one is correct, while the 3rd is not.

But I feel the first sentence is wrong= "She sings like her mother"
We are comparing her singing to her mother.
"She sings" is a clause, isn't it?

I agree that the first sentence is problematic. You can, however, write the same information using "like" or "as" just depending on how you construct the sentence.

Try this instead: Susan, like her mother, is a good singer.

Or:
Joe, like Mary, has a cat.
Joe has a cat, as does Mary.

Both of the above are correct - I just have to write the sentence differently.
I can't say: Joe has a cat, like Mary. I have to put Mary over near Joe if I want to use "like."

You can say "Joan sings like her mother," meaning, "Joan sings in the same way as her mother does." Don't let yourself get trapped by the semantic argument too much: "am I comparing Joan's mother with Joan, or am I comparing the way Joan's mother SINGS with the way Joan sings?" In fact, you're arguably doing more of the latter, but just as Stacey says, you can often construct the sentence EITHER with "like" OR with "as." The bigger issue is structural: first of all, never put a tensed verb after "like." For instance, never say "Joan sings like her mother sings." Secondly, if you use "like," try to put it as close as possible to the noun you're doing the comparison with, so that you avoid ambiguity ("Joe has a cat like Mary."). This second point leads you to put "like" constructions near the front of sentences on the GMAT, since you're often doing a comparison with the subject.

Incidentally, there IS a meaning difference between "Like her mother, Joan sings" and "Joan sings like her mother." In the first case, what you're saying is that Joan engages in the same activity (singing) as her mother. In the second case, you're saying that Joan engages in that activity IN THE SAME WAY as her mother does. However, to my knowledge, the GMAT hasn't tested this distinction -- both forms are correct, after all (they just mean slightly different things).

Thanks for the clarification.

Your response says "The bigger issue is structural: first of all, never put a tensed verb after "like." ".

Then why is "People like you inspire me" correct? "Inspire" is a verb here. Please clarify.

because it's not part of the same construction. that construction is

(people like you) (inspire me)
i.e., (noun phrase) (verb)
...so the 'inspire' is TOTALLY independent of the 'like' construction.

in the faulty constructions quoted by chris above, the verb is actually the latter part of the 'like' construction. do you see the difference?