LLC) between myself and a partner - what are some key things to incorporate in the operating agreement (not in cookie cutter entity formations)?

But an attorney would provide articles of incorporation and an operating agreement along with the LLC to designate it for your tax or legal needs that are important to you.   

Unless you incorporate as an s Corp which I just did, but you pay another $600 to $1000 to your cpa so you better be making at least 100k in profits a year to make it worthwhile. 

You should be thinking more about where do you want to live your life and then figure out how to incorporate your real estate investing journey into that.

That way I could incorporate possible monthly income generated into my income.

Understanding how money works, and how when incorporated into compounded returns (always).

Can the third be incorporated into the second and rented as one big unit?

I would listen to the BP Podcast with Thach Nguyen on how he knocked on one hundred doors a day , five days a week for ten years and that got him one million USD per year from that ACTIVITY.Make sure you dont miss the part where he says one home seller let loose a dog on him and he had to get attention at the hospital from the bite.I would also pay attention to the Tom Hopkins Champion formula to embrace rejection on pages 110-125 in his book Mastering the Art of the Sale.Especially the part where he says , you are paid for each rejection you getThen TAKE ACTION, make the calls, follow up leads, ask for referrals, make offers, buy properties, choose your exit strategy etcin making calls i would attempt to incorporate "negative phrasing" as taught by Steve Trang, to locate buyers, sellers, private money lenders.I would also set a saving rate as taught by Anthony Robbins from book Money, master the game, becoming of an investor, taking advantage of the power of compounding I would also keep in mind the 10000hour rule from Malcom Gladwell's book, Outliers reminding myself that attaining world class takes commitment

Personally, I do incorporate that language into the lease and will make exceptions on a case by case basis.If tenants are neglectful I will force them to remedy the issue.

This is my first partnership multifamily deal after purchasing and renting my own properties, and I'm a bit lost on this topic.My goal is to have equity ownership, take advantage of depreciation, and hold the property in the LLC long term, while collecting distributions and paying applicable taxes on those distributions.My intention was to assign % ownership when the entity value was $0, like can be done when founding a company prior to incorporation.