If you can demonstrate that your year-to-date capital gains are in line with previous years and you have documentation to support this (such as brokerage statements and tax records), an underwriter might include it in the income average.It's crucial to work with a knowledgeable mortgage broker or loan officer who understands your unique financial situation and can navigate the complexities of underwriting capital gains income and 1031 exchanges.

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

Document everything with pictures and video.

HOWEVER, want to avoid/minimize setting up a new company and filing additional LLC and other related documents (want to avoid extra work additional docs would create). 

We close with attorneys who draw up all documentation, trusts, and act as escrow.

Unless specifically allowed or required by Section 8, this is often illegal both for the tenant and the landlord and you will often be required to sign a document to that effect. 

Do you have some kind of supporting documentation?

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

Go to Etsy and search for "rental property tracker," and you will find hundreds of nice spreadsheets to track 10-20 rentals, usually for under $10.Software has extremely helpful features like online payments, marketing syndication (click a button, and your property is advertised on multiple sites), electronic document review/signing, maintenance tracking, and owner reports.

Change Orders: Detail the process for handling any changes to the scope of work, including how they will be documented, approved, and the impact on the timeline and budget.