While I think I'm somewhat understanding what you are trying to achieve (i.e., one row of data per property), your approach is confusing me. So, I have a couple of questions for you:

1) What version of SSRS are you using?

2) It looks like your dataset is SQL based (rather than OLAP, SSAS)?

3) I'm not sure why you have 20 datasets. Wouldn't a single dataset query that joins your data together be a better approach? A single dataset query could be written so that only one row per property is returned, I would think.

--pete