How to approach realtors to find off market deals?

[Nik Moushon]

I have a realtor in mind that I want to approach about helping me find specifically off market multi-family property to buy. I'm not sure how I should approach and bring up this topic. I have experience dealing with realtors for SFH but not MF, is there anything different? In my mind the answer is probably not much but I'm not a realtor.

Also is it wrong to talk to more than one realtor, since I'm just starting out and have not built up any working relationships with anyone, to increase the odds of finding more property? I am very much against burning bridges, even if they deserve it, so want to start this off right. 

Thanks in advance for the help.