There are issues that come from buying data such as data wastage and redundancy, for this reason, we recommend that you ask your suppliers to outline their data wastage policy with regards to duplicates, wrong numbers, fax numbers, unobtainable numbers, contacts who have left the company or are deceased, as well as any pre-existing contracts that your business may have.
With this in mind, once you have appointed a supplier, it might be worthwhile creating a suppression list of contacts that you are already engaging with to save being provided with multiple duplicate leads.