I believe this is correct. In the sentence: “I always find friends in unusual places, for example, my friend and I met while teaching an aerobics class to senior citizens.”
I would say that the sentence is correct the way it it because the phrase “for example” is not necessary, thus it is offset by commas.
Others ways I would write the sentence:
I always find friends in unusual places. For example, my friend and i met while teaching an aerobics class to senior citizens.
I hope that this helps clear things up for you:)