I’ve used Facebook marketplace to purchase Phonak hearing aids. This allows me an opportunity to meet the owner and examine the aids. Transactions
have been good. Speaking exclusively about Phonak devices, you may have an issue if the aids are still under warranty and the rechargeable battery or batteries fail. Here is why.
I bought a pair of Phonak Lumitys from the relative of a deceased veteran. I had no problem until after a year of wear, then a battery failed. Since I was not the original owner, Phonak was not going to honor the warranty. Phonak maintains a database of purchasers and serial numbers to who equipment was originally sold. Additionally, since the aids were originally issued by the V.A. the aids needed to be returned to the V.A. for repair. Apparently the V.A. has their own repair facility independent of Phonak. No one else wanted to repair the Phonak aid and was told they must go back to Phonak.
I was lucky to have an audiologist office pursue this on my behalf, got Phonak to repair the aid under warranty and have the aids registered in my name should the aids need service in the future. Despite the headaches, my savings with the initial purchase was substantial. Out of warranty battery replacement for Phonak can run $300 - $500 per aid
I am reading in this forum that some audiologists will not program pre-owned hearing aids, so keep that in mind.