Berkeley and Mistletoe are competitive neighborhoods for finding rental homes. Sometimes homes are advertised with a real estate broker and sometimes they are advertised privately via Craigslist and other sites. It's advisable to contact a professional who works in the area who can get you adequately prepped should a match hit the market. You have to act fast here.
Another good resource is Lovely, which combines various sets of rental information. Find it here: http://livelovely.com/