Database Expert Needed

We have a medical clinic that is moving from Allscripts to Athena. Their existing database is 1.5TB with an images folder of 3TB. The Athena team says that this database is extremely large and is going to cost the practice multiple thousands of dollars to house. The practice would someone with the proper knowledge to go in and remove old patient data and shrink the existing database as much as possible before the data is migrated. I am not sure how possible this is, and am looking for someone with the proper skills to help.