This is a great forum with very knowledgeable members that will help to guide you in the right direction.There are a few self-contained guides that you can access here: https://www.biggerpockets.com/guidesAlerts can be really helpful too: http://www.biggerpockets.com/alerts

Are you going to use property management or will you self manage?

I accept a lot of those issues are both self induced and partially inherit. 

With a little self reflection, you will begin to learn your strengths, weaknesses, limitations and preferences.

Plus, you are probably talking $1,500,000 to 2,000,000 purchase price to buy a 20 door apartment with $300,000 to $400,000 down... so while I imagine that thought was just conceptual... start small... 1 property... maybe it has 1-4 doors... its often more about what you can find, that is at a good price, that you can afford, that will rent the best.We are at 40 doors in 3 years, and it's a number we have been trying to hover at, because it is a size we can self manage, and that is what we are trying to do for the moment.  

Your profile doesn't say where you are located, and I don't know what areas/states/towns you are looking in....Since you are a self-proclaimed newbie, working with a buyer agent might actually be helpful to you.  

We self finance so our relationships are limited to savings and checking. 

Look up post    "Self Storage- Setting up LLC";  Also "Self Storage- LLC operating agreement.use the Search magnifying glass above.

Sounds like you are already aware that you need 2 years of tax return proving self-employment income - no traditional lender is going to accept bank statements.

Do Self storage.