The loan application will ask about the assets you need for the purchase (down payment, closing costs, and reserves), and you will need documentation for those accounts (most recent statements). 

I would probably start monthly or bi-weekly "safety inspections" to A) document any lack of evidence of risks/issues to the tenant's safety to be prepared to legally defend yourself in the future, and B) to monitor for new/worsening damage to the unit.

Find the downloaded file and click Upload.This should show the document in Google Sheets after.

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

Since contacting 311 hasn't been effective yet, definitely try submitting your complaint electronically with the pictures you have taken.

Do a GOOGLE search, get the tax information, read through any relevant documents the seller has provided.  

Furnished Rental Checklist: https://docs.google.com/document/d/1RzTpNu1Vsm1_PJxPa_uTk5vL...2.

Honestly, before the paid subscription, lots of tenant messaged me for showing and submitted application as well. 

The contract shouldn't affect your basis, that will be based on what you pay for the property (unless there's some money changing hands outside of closing, which probably wouldn't be documented in the first place).

@Jerome MorelosIt will be similar to what you sign with a bank, there will be a note (which is the iou which states how much you can borrow and at what terms and length)Then there will be a deed in trust (assuming California) which is a recorded document that uses the property as security.