We've compiled and vetted a list of duplexes (about 75) that meet all our criteria and which we'd consider being occupant-owners of.Planned next step is to send them letters stating who we are, what we're trying to do, and letting them know we'd be interested if they'd like to sell.Any experience or suggestions for how to format (handwrite vs typed, etc) and what points to highlight?

There is also now snap/click vinyl planking as well, a little more expensive but faster to lay without the glue mess.Not sure on the pricing without seeing what needs to be done and you certainly dont want to replace the mess you have now with a future mess. ( same material )  As @Jaron Walling ceramic is another great option but going to cost you quite a bit more upfront.  

I purchased my first rental on August 30th, a duplex that already had tenants. 

Currently renting an apartment in a duplex and am looking for a better tenant than the ones that just left.

The buyer if my duplex had asked torepair the overhang on the roof, and fix the outside staircase so the bank would approve his loan.  

I recently moved from a duplex where I was house hacking in Maine to Idaho.

Any tips for success for investing in the west side of Detroit's real estate market (especially lists of due diligence questions to ask before purchasing duplexes there)?

Oakland has strict rent control laws, like San Francisco, Berkeley, and many other cities, however there is an exemption for both duplexes and triplexes when the owner lives there as their primary residence.  

Read "Rich Dad Poor Dad" and working my way through "Cashflow Quadrant" and the other books by Brandon are sitting in my queue.Currently struggling with deciding on an area to invest in, already decided to invest in b or c class, not sure about duplex or SFH yet.

For clarification are you meaning 5 or more units per property or as in buying wholesale duplex, tris, and quads?