>1-For young men looking good is important.
>2-For young men to look good is important.
>3-For young men, looking good is important.
>4-For young men, to look good is important.
>I think all of the sentences 1-4 are ambiguous and could have any >of the following meanings:
>a-Young men think it is important that they look good
>b-Young men think that it is important that others or certain others (presumably women) look good
>c-The speaker believes that it is important that young men look good.
>Is that correct?
First of all, there is no difference between 1 and 3 or 2 and 4. Introductory prepositional phrases are often set apart by commas; however, many authorities (including English Plus) say that it is optional if there are fewer than four words in a single phrase. Still, some authorities do use commas even for shorter phrases. (Note that all authorities note the need for a comma in order to avoid ambiguity.)
It is impossible to stretch the meaning of the words given to say “b,” unless it is a short statement or answer given in context. There is no subject for “looking good” or “to look good,” so it would not mean “b.”
They could mean “c,” but without context, they would have to mean “a.” If the speaker meant “c,” he would put the prepositional phrase at the end of the sentence, closer to the word it modifies.
Remember, most prepositional phrases modify words or phrases they are next to. Sometimes introductory adverbial phrases will modify the verb, but that is unlikely here with just a linking verb unless the phrase is one of time or place.
Perhaps in certain contexts, such sentences could mean “b” or “c,” but without any context, the only meaning that makes sense given the words and word order is “a.”