title: RETS or not RETS
body: <p>We want to build a MLS application. We want to use a real MLS service as data source. What will be a better solution: using RETS directly or use a 3rd party data service to pull MLS data for us then query them for data? 
  PS: If we want to use RETS directly, are there like sandbox services we can test our client application?</p>