Best time of year to lease Loaner MB C-Class?

What’s the best time of the year (MF/RV/etc) to lease a loaner C-Class Mercedes? (e.g. shortly after 2018 release for 2018 loaner? Or go for 2017 model at that time? Or wait a few months?)

What are the rules on whether they qualify for new car incentives (MF/RV/etc.)? Do you just search online inventory for CPO under 10k miles? Do fleet incentives apply to loaners?

I guess same questions for BMW as well.

Hoping to lock down a loaner C Class with distronic (if they exist) sometime later in the year.

Would be curious to see what other hackrs have to say…