Negotiating Realtor Commission?

[Luke Johnston]

Hello,

I'm working with a buyer's agent to make offers on properties. I'm making an offer on one SFH for about $170,000. We're also making an offer on a 4-plex for over $500,000.

Given that the 4-plex is more than 3x the price of the SFH, would it be reasonable to ask my realtor to do the 4-plex at a lower commission rate?

If so, what would be a rate to request that would be reasonable?    

At a 3% buyer's agent commission rate:

The SFH = $5,100 Commission to buyer's agent.

The 4-plex = $16,000 Commission to the buyer's agent. 

How much more work goes into the contract on the 4-plex?   Would asking for a 1.5% or 2.% commission be acceptable? 

Thanks for your advice/feedback.