Most Helpful Guy
Next time he asks you say "OK, I'll do it just this time but we're having a talk about this."
When you see him (face to face) tell him exactly what the problem is ( it's taking your time and your money). Let him know you won't respond to either his desperation or his laying guilt on you.
If he ever requests again politely say no and remind him of already having the conversation. (Let him pout, lay on guilt, whine. . . you're not his mother).