I remember hearing about this during a BPP but it definitely seemed complicated and I have no idea how I would even proceed with such an endeavor.

Now, that all said, this is the real world, and all the numbers are  a lot more complicated with a WHOLE lot more pluses and minuses --  loan fees, points, PITI, commissions, repairs, rental income (hopefully!)

If accounts are commingled, it gets very complicated.

There are a lot of these in places like Belize, Costa Rica, and the Caribbean Islands that are tempting but are ultimately too complicated to touch. 

The complication is I have 4 units and if I put I'll put all 4 together.

Both of these seem like ways to make a straightforward deal exponentially more complicated. 

But the stronger legal protection you want, the more complicated and expensive it gets.

Also in judicial states you have to certify the amount and its much easier to do with a servicer, then there is the issue of whether you need a license to service in that state.

its not that complicated if you know the checklist / order of operations and some of the pitfalls to watch out for.seller pays agents if there is a commission agreement in place.  

There is a somewhat complicated formula that takes into account the property type (number of bedrooms) and the local utilities and the tenant's income to then spit out a number of what that tenant is able to afford for rent and utilities combined (a maximum affordability amount).