Due diligence!!! Where to start? Where to end?

[Mercedes D carmouche]

Ok, here is the deal. I am looking at investing in my first income property, three multi buildings and possibly a single family if possible. 

     My dilemma is due diligence. Where to start, and how do I know I have have checked into everything there is to check? 

     So far I have ran numbers like the pod cast have shown, (didn't use the bigger pockets calculatetor). I have done the 50%, 2%, and the 1%, but with the numbers realtor has, which I hear are not good to use, and some say it's ok to use Soooo Blah I'm stuck. So what dose your due diligence check sheets look like?