first of all, sorry for the English but I'm still far away to keep it in Swedish

My name is Pierluigi and I live in Solna. As all of the people here, I really felt in love with the Model S.
What I would like to know is how exactly work the "tjanstebil", in particular applied to Model S. Is it convenient to buy the Model S in that way?
How much is the minimum monthly salary level we can consider good enough to afford a Model S 85 as a tjanstebil?
Thanks in advance to all of you that can help me understand if the dream can become true or not!

/Pierluigi