Is there any difference between in the start of something and at the start of something? Not long ago I would've thought that in the start of was incorrect, but in the 11th episode of the 6th season of Friends Joey said exactly that. Here it is:
Joey: That’s right! I helped you guys out a lot in the start of your relationship. Huh? I helped you guys sneak around for like six months, and I looked like an idiot! And I was humiliated. And I only made 200 dollars!
Would the meaning of the sentence change, if he said at the start of?