I've asked my clients a similar question and have developed tools for them to minimize this, but I find there are a few different types of clients.Manager managed - these folks have no issues as they simply upload their year end statement from their property manager, their 1098 mortgage statement and any other one-off expenses they may have paid for outside of the management company. 

That 2nd requirement is  what makes it close to basically impossible with a W2 job.

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

@Bob Dole please tell me you have a CPA and you're simply educating yourself so that you can verify what he is saying is correct? 

This can be done, it just requires finding the right lender.

Newer septic rules also require enough land for two septic tanks per each one you are required to install.

Most non-FHA loans will require at least 15% down but you'll have to have amazing credit.

This requires a dedicated effort sourcing and analyzing hundreds of deals to find the one or two worth pursuing.  

I'm also a licensed mortgage broker with a lot of fix-and-flip programs, including some that require as little as 10% down on the purchase price, and provide 100% of the rehab funding.

What kind of seasoning is generally required as it relates to the rents/revenue as it relates to servicing the note, etc...I currently own one PadSplit (acquired via Subject-to) that has been up just over a month.