I think it would depend on what you need the system to do for you. I really like Rent Manager because of the support, training, and the simplicity of using it. I've never used buildium so I really don't know how it would compare side-by-side.
As for the CRM, we use insightly. There is a free version of it and the paid version is about $10 per month per person. I use the paid version but I think most people could get away with using the free version. We have storage requirements that exceed what the free version allows.