i always go internet dept/email for best figures for the last 10 years. ill share what i did with my family member recently in getting their b class.
we walked into one dealer initially, did a test drive, and was given rough numbers $5k down, $400 monthly to start. the rep says he can try to match a deal if we find one. i emailed a few dealers from santa monica to los angeles to ontario and the best quote that i received was $1k down (im learning on leasing, try to go lowest down), $399 monthly for 36 months 12k miles a year. my family used the quote to find the one they want and a dealer who will match the quote. they end up with a loaded (msrp $49k) b class for $1k down and about $390 a month including taxes and fees already.
hope this helps. good luck and have fun shopping.