Visa's etc

Can anyone advise me please?
We would like to have a friend from Turkey to stay with us over christmas/new year, it seems he has to get a visa. I have the relevant paperwork (all in english) to send to him and have written a letter to send with his application stating that he would be staying at my home address for a 2 week period and returning to Turkey at the end of his stay.
Is this enough? Is it easy to get a visa to visit us from Turkey?
Any other info would be gratefully received.
Thanks in advance.
We would like to have a friend from Turkey to stay with us over christmas/new year, it seems he has to get a visa. I have the relevant paperwork (all in english) to send to him and have written a letter to send with his application stating that he would be staying at my home address for a 2 week period and returning to Turkey at the end of his stay.
Is this enough? Is it easy to get a visa to visit us from Turkey?
Any other info would be gratefully received.
Thanks in advance.