Goes up and down of course but that's a pretty solid number to use as an average.

If you are in fact referring to gross rents, then yes you can get gross rents well above that but after all expenses, includeing debt service, PM, maint, cap ex reserves etc, a good deal is about $100 - $200 a door in pure cashflow. 

Vacancy can be very expensive. 

It is much more important to get to know what a PM's experience is, how many years they have been managing properties, are they also an investor, what types of owners they work with, how many total units they manage, what their largest property is, what class of properties do they manage, how do they handle tenant communication, maintenance requests, expenses, do manage commercial or residential, and what type of software they use.Just some advise from a seasoned investor and property manager, The First Question That You Shouldn't Ask is, How much do you charge?

While they do deliver results, they are expensive. 

Can anyone provide (or provide a resource where I can find) average CPM, CPL, and CAC for the following marketing channels: Email, SMS, Direct Mail, Cold Calling, and RVM?

(My only current expense is ~$100/month on gas)

I aim to purchase two apartments outright in either Brickell or downtown Miami—properties with minimal HOA expenses. 

A major electrical expense has basically no ROI.   

There could be some exceptions, like if you had a lot lease in a highly in demand are, such as on a lake or in a very expensive market.