Mercedes C300 4Matic Coupe 2017

I’m so glad I found this website. I am interested in leasing a C300 Coupe. I have been told that I need to wait a couple more months for 2017 C300 Coupe cars in dealership loaner program to be available to lease. Can you please let me know how much off the MSRP I should expect on a car that was in their loaner fleet? I don’t know miles yet obviously but have leased loaner and executive cars before and they typically have any from 2k-4500k miles on them. I do less than 10k miles per year but looking for negotiating knowledge on loaner cars. Also, it seems I should negotiate MSRP based on purchase assumption first, then tell them at the end I want to lease?

Thanks in advance!