Usually the bank will accept what is owed to them and allow you to take payments if you fill out their loan assumption application and are approved.

How will a newcomer like me get started now?

Most City Planning Departments have what is called a Pre-Application process.

For example: I wanted to start making and  a tenant application and start building business credit (because i heard business credit is stronger than my personal credit).

Trash, sewer, HOA if applicable, etc.

- Prospective tenant replies- Email template with video (explaining application process), 3D tour, and a link to the Zillow listing, where tenants are instructed to apply.This almost certainly adds a few days on market for the properties, but selects tenants who inherently 1.can read 2. do read and 3. follow instructions. 

We are scrambling to get more vacant apartments for all the applicants.  

But after one month, only received one unqualified application.

But I showed him my first property, the numbers, my Cozy account, how I was screening tenants, my leases and applications, bank accounts (showing I was running it separately of my personal finances), and some bigger pockets calculator results.

Im assuming you will not have a Property Manager make sure you have your systems set in place beforehand (concerning how to handle maintenance request, rent, applications  etc) and that you understand your State Tenant & Eviction Laws..