In the MLS there is no 1542 s marston but there is a 1545 s marston that has just been recently rehabbed and is for rent at $750 a month. Maybe you had the wrong address. Please feel free to give me a call and we can make an appointment for you to take a look.
To answer your question, 1542 S Marston St does not appear to be listed for rent on the MLS; but that does not mean it is not available for rent. Your best bet would be to call the number on the sign (I'm assuming there is one, or this question would probably not have come up).
If you're having trouble, please let me know and I can try and find some alternative options for you.