Estimating Landlord Expenses

[Jiten Voralia]

This is my first post having only recently discovered Biggerpockets. I really want to get going on SFH using Buy-hold and BRRRR strategies. The various calculator are a fantastic resource which I've been using to try analyse a bunch of deals to develop my own knowledge and experience.

I've been struggling to quickly and accurately estimate the Variable Landlord-Paid Expenses for rental properties.  Just wondering how people go about this?  For an initial review would you suggest to simply use the 50% rule and only if the initial metrics pass would you due further due diligence such as request as expense breakdown from the seller?  

Any feedback from current investor on how good a proxy the 50% rule is for SFH? Thanks