harry potter - How does Charlie's wand work for Ron?

On the train to Hogwarts in the first book, Ron says he uses Charlie's old wand. I have two questions:

1. 
   

   Doesn't he have to kill or disarm Charlie to be able to effectively use Charlie's wand? How could he do this with no wand.

   
   


2. 
   

   Didn't the Weasleys just have to buy Charlie a new wand anyway? Why didn't they buy Ron one? Charlie would be fine with his old wand, unless he drove a car into the Whomping Willow.

   
   

Here is what Ollivander says:

"Much also depends on the wand itself. In general, however, where a wand has been won, its allegiance will change." ".....the conquered wand will usually bend its will to its new master."

Answer

J.K. Rowling has answered your first question:

Stephanie: If the wand chooses the wizard, then why do wands work when passed down from father to son, e.g. Neville had his father's wand

J.K. Rowling: As established by Ollivander, a wizard can use almost any wand, it is simply that a wand that chooses him/her will work best. Where there is a family connection, a wand will work a little better than a wand chosen at random, I think.

_{http://www.accio-quote.org/articles/2007/0730-bloomsbury-chat.html}

Charlie was already working by the time Ron enrolled into Hogwarts. So Charlie could afford another wand.

We never read about Mr. and Mrs. Weasley borrowing money from their kids, instead they purchase used things for their kids. It is possible that Charlie might have given away his wand to his brother. To reduce financial burden on his parents.