Make sure to set up boundaries because if they know where you live (one wall away) you don't want them knocking on your door at 2 am especially if they are college  kids because they will be up.As far as advice, some more info about the deal would be helpful.  

Probably should door knock after they see your mail.

Knock out the 90% property first.

Did people ever react negatively to your door-knocking?

I forwarded this along and they have now gone silent.I was at the apartment today to talk to the other tenants of the same apartment (it’s one apartment but two different sections of it), I saw a dog bowl and leash and asked the other tenant if they had gotten the dog and he stuttered and said it was for his parents dog when they stop by every once and a while.I walked around to the other section of the apartment and knocked on the door 3 separate time and waited 3-4 minutes overall with no answer (both cars were there).

I also think there is a real sweet spot for the 6-15 or so unit properties (maybe 5-20 unit, depends on the area)  They are too big and need a commercial loan so that will knock out much of the competition you will have for 3-4 unit buildings. 

You have a great income, knock out that student debt and start going nuts investing. 

You need partners that have strengths where your weakness is, which is focus.Good luck, clearly you have skills, you just need focus and you will knock it out of the park.

I want to get him started on door knocking and cold callng.

Or even when I door knock most of the homeowners are shocked that I'm coming by.