I suspect that within real estate more and more new online estate agents are setting up google adwords accounts and flush with investors money are throwing money at adwords to try to get to position 1.
When this happens focus on quality, by which I mean the quality score, enhance the user landing page experience, ad relevancy, etc etc. Try to get most keywords have a QS of at least 6/10
Also highly target your visitors, demographics, location, themes - this will further boost QS by increasing ad relevancy and landing page experience, and thus reduce your CPC and ultimately the CPA.
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PS, Just looking at your first post;
If you quality score is going down then you will have to increase your bids to keep your FPR ( First Page Rank ) this is most likely what is happening and so the solution would be described above. You will soon understand how important QS is to google..lol