Gdpr could be an issue.
Last time I sold some (only about 15 customers, value about £300 every 8 weeks, sold for £600) I told the customers in writing I was downsizing in a couple of months and offering their contact details to a trusted window cleaner.
I included the following paragraph.
Understandably you may not wish to have your details passed on even to a highly recommended window cleaner, so please let me know with 14 days if you would prefer me to give the recommended window cleaner's number to you instead.
No one caused an issue and one even asked me to pass on a back gate key!
It's the way you tell'um!