If the CRM-like functionality is important then it would be best to find a suitable marketing automation system (Goldmine / SuiteCRM) which has a plugin for real-estate listings, else the WordPress plugin approach is perhaps the simplest way forward.
I have a few real estate brokers as client in India and I suppose the business model is the same across geographies. If you like, I could do an online demo of the solution that I have provided to my clients here.