"I am waiting for you."
Translation:Yo estoy esperándote.
Por vs para: My way of summing up all the rules is "the means to the end" Por is the means, para is the end... Por is the method/exhange/pass through by which you arrive to the end point/destination/deadline. Quick and dirty and incomplete but hopefully this way of thinking about the confusion prepositions helps someone!
Wim y los demás: No one has given a complete answer. Esperar means wait or wait for, depending on context. No por, no para, no a. Esperar takes a direct object. You cannot say a ti, because the personal a goes before nouns, not pronouns. So the te can go either before the main verb (as in the DL translation above) or stuck to the end of the present participle aka the gerund, with an accent on the a to keep the stress in the right place. Estoy esperándote. There is no difference and both versions are used everywhere.