What documents do they require, what credit scores do they allow, how do they verify previous rental history, etc.?

https://www.portland.gov/phb/rental-services/documents/tenan... 

Hi folks, As the topic states I'm looking to learn everything I can about the City of Philadelphia and its real-estate market. I'm looking for someone is willing to spend time with me and maybe teach/talk/travel aroun...

That will allow good analysis of sale price appreciation and rental history. 

Use an agent to help you get qualified tenants and documentation in order.

I would get an attorney or title company involved to create your loan documents to ensure they comply with the law and cover all the aspects you need.Another method that is likely your best bet to take on investors is to create a joint venture (JV).

If they say "No" then ask them to support that with documentation to avoid a boiler plate response. 

Is there a specific document that I will need?

We are willing to provide additional documentation to support our request and discuss any potential steps to ensure a smooth and fair process for all parties involved.Thank you for your attention to this matter.

Even someone without enough credit history to have a score might have pertinent information on the report.