I suggest you call a few agents and select one you feel comfortable with and will represent your best interests. It will be very difficult to find you something in a great area for $400 a month. You will probably have to double that to find a 1 bedroom that would work for you. I do have one roommate needed situation currently but it is in Boca and would probably run about $650+.
If I can be of any assistance just let me know.
Always at Your Service,
Tom Priester e-PRO
"Results Driven Real Estate"
Keller Williams Realty
Suggest you go to google and google West Palm Beach rentals for $400/mo. And look thru all the rental offerings. That is a really low monthly price.
Best wishes on your search.