Denise,
You never lose by knowing more.
Landlording is a time honored investment strategy that will make you rich... but, you have to know what you are doing.
I recommend that you work on improving your knowledge and skills first, and then look to invest.
As far as the St. Louis market, I have no experience there.
Duplexes are great, in that one side often can pay much, or the whole, note. Thus, when you have a vacancy in one unit (half the rental), you still have income coming in.
A single family home is the Rolls Royce of rentals: the lifestyle experience everyone wants. They are the easiest to rent, and sell, if you need to.
First work on building more general rei information. Then look into the particulars.
Hope this helps...
Hal