How to discover multifamily commercial deals

Fellows, I am Suhaib, and am pretty new to real estate investment. I am interested in commercial real estate, especially multifamily apartments. 

For all of those who are in the same real estate space. what means do you use to discover deals?

There are some open listings like LoopNet, and Crexi which I was told are not the best deals to look at. I have looked at costar which is too expensive for me at the moment. 

I am wondering how you find these off-market deals. 

For off-market how do you approach? I read that one of the strategies is to connect with the multifamily real estate broker in the market you are interested in and build a business relationship with them, for them to send you the off-market leads. How strong is this strategy and will it work for first-time investors?  I am kind of now sure how to discover the brokers in any market.

The other strategy, I am thinking of is to filter the properties which are not for sale and reach out to the owner/llc if they might be interested in selling the property.  How do you find such not listed properties and how do you find the contact (PM/owner )contacts

Regards

Suhaib