Especially since you don't have a signed document.

I am so glad you made this post! 

They say they have plenty of time and they will be able to close by then, but I've never seen this slow of a process. 

I work as a firefighter while finishing college, and over the past year, I’ve immersed myself in this world—reading books, listening to BiggerPockets podcasts, and diving deep into everything I can learn.

Wondering isn't the owner suppose to disclose this fact.

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

This will become a significant cost as you growFinally, to help put this into perspective, assuming you will be looking for deals and not just buying at market price, it will be difficult to find so many properties.  

My uncle has done 84 percent for the last 14 consecutive years (these numbers can be proven  and have been well documented) .

Agree with this post!

I would suggest reaching out to the agent you had already worked with in the past as this is a common thing that happens in leases.