@Adam Stout Welcome to the BP Community, this place has a world of knowledge and you can literally leverage it to the max for all your real estate endeavors.
So to answer your question, I'm not an investor in the St. Louis market, but what I can tell you what will work in any market if you're willing to put in the work like we all initially had to do. My advice if your looking for any type of investment is to take action and in relation to your 4 unit MFR I recommend to start attending local REIAs/local events to network, get on the phone and start calling realtors who have listings for smaller MFR's because they are more prone to working with investors, start "driving for dollars" as we call it on BP which is basically driving around and finding properties off or on market, call all the local banks (preferably smaller credit unions/family owned banks) to see if they have any REO's on their books, check craigslist/zillow/redfin/etc to get a feel for the market and most importantly is to start analyzing the properties. I recommend using the BP calculator or your own spreadsheet (I use both) if you already have one to run the numbers so you can get a feel for the potential returns based on "YOUR" specific target market which is so key. Once you've analyzed a deal and unsure of the numbers, no problem, post it on here and we will all be here to help out.
Best of luck and if you have any other questions feel free to message me at anytime!