NIE NUMBER

Hi all

We are moving to mazarron later this year. Would be grateful for any advice 're NIE NUMBER APPLICATION.  I know the procedure for applying for one but my son is coming with us and my main question is do you actually have to have a job contract to obtain one or can you apply for one saying you need it to be able to work. 

Also does it all haveto be completed in spanish or can anyone advise how we get help on this including cost wise etc.

We are UK pensioners so only need it for bank accounts 

Any help gratefully apreciated. 

Thank you all. Eve