I read about direct mail but I wanted to have more experience before I went knocking doors down.

It could have been that one property manager and I really have no problem knocking on doors but like I mentioned I have the best renters and I live in AZ which is a very landlord friendly state where it only takes me 20 days to evict a non payer and I do not need an attorney.

Door knocking, cold calling, driving for dollars. ect

I would welcome suggestion/opinion on some of the questions below(1) Is it OK for me to knock on the door and politely ask owners to vacate? 

Or is it just better to knock and face the disgruntled homeowner.5 - Does an investor just line up credit first and then go into the wild.6 - If the credit lined up via a bank/credit-union is for more than the price of the home, does it still require your own 20% down.7 - Duplexes/Triplexes/Quadplexes don't seem to be listed very often on many sites.

Paynearme, for one.Have you gone over to the place and knocked on the door? 

You could also put some type of contingency in the offer that will allow you to back out, but may times great properties are scooped up by investors that buy cash and as-is, so that could knock you out of the running. 

If these are the only 2 you are going to mail to and really want to make contact, and can't knock on their door, go big.

I'd prefer to minimize the amount of tuition I pay in the school of hard knocks!

Would you knock on their door and inquire if they were interested in selling.