When someone says 我帮你 (I help you), does it imply they will assist you in doing something, or they will do it for you?
"帮" in "我帮你" is a shorter form of the verb "帮助" (help)".  "我帮你" means "I help you"


Example: 

A: "who will help me?" - "谁会帮(助)我?"

B: "I will help you" - "我会帮(助)你"


  "帮" in [我帮你 + verb phrase] can be an auxiliary verb for "help" or a function word for "for (in behalf of)". 


Example: 

"我帮你對付他 = "I help you to deal with him" or "I deal with him for you"

"我帮你拿着" = "I help you to carry it" or "I carry it for you"