Assuming you are looking to live in and rent (SF house hack) I would start by finding the areas you would like to/be comfortable living in then look into the pricing to buy and rough rents in those specific areas.

My goal is to continue to acquire rentals but ensure that they are cash flowing comfortably...

Samuel,Glad to see new investors taking the initiative and getting out of their comfort zone!

It can be a little awkward if the tenant is there or if the place isn't in perfect condition, but my feeling is that its more important to get the unit re-rented ASAP than to make everyone feel 100% comfortable.

I’ve been looking at properties and would analyze the deal just to practice the “math” to make sure I am prepared and comfortable when analyzing my first property.

Get comfortable in the environment first,...then get involved in it.

Last night, 2 years in, I sat down with a note pad and calculator Andrea figured out exactly what my expenses were and would be going forward and how much I’d need to make passively each month for both myself and my wife to quit our W-2 jobs and be comfortable.

You'd want to be comfortable if you were a tenant right? 

It did take a few deals for them to learn what I do and get comfortable with some of my riskier deals.

I would go as big as you feel comfortable with, if that's a 20 unit, go that route, if it's a 4plex, do that.