how much can I "Afford"? :-)

[Steve Miller]

I'm new to Commercial and finding it challenging to figure out how much sales price I can afford. Having bought and sold 5 SFRs over the last 15 years I'm not new to RE. I am new to commercial. I see properties I like (4 unit bldgs.) yet when I run the numbers with what I intend to put down ($50k) the CashFlow/ROI is either negative or a few dollars at years end. There's a 4 unit I really like, it listing price is in the ballpark of fair ($1 mil) and I like everything about it. While I am firm in the reality of "its worth what it's generating Now", the upside is that rents can be raised and I'm confident even with a fair rental rate increase, the units will get rented should the cheaper tenants leave. Where I'm at a road block is

A. making it work with $50k down and B. Can I even expect to get a loan with such a small down payment for $1 million?   At the moment all 4 units are rented but quite below market rates. 

Thank you for your input!

Steve