Deduping a list of property owners (Excel Online)

I need a freelancer familiar with list scrubbing in Excel to consolidate duplicate line items.
The list has 1000+ rows and the final result will probably be around 600.
The idea is that one property owner that owns say three properties receives one offer letter for his properties instead of three separate letters.
I expect this work to be done within three days, the work itself shouldn’t take longer than three hours.

I might have subsequent work such as mail merge that I’ll post separately.