My main gripe with sellers on eBay/marketplace/wherever is those that have found a camera in their Grandad's loft, they have no idea what they are looking at, it's condition, whether it works at all, whether the battery compartment is swollen with a 30 year old battery, and just list it up for absolute top dollar.
Then the other type that list the broken stuff as untested, when they clearly have the means to and routinely test their other 'working' items.
Facebook marketplace is the worst for that given it's free cost and ease of listing. I've seen too many bundles of seized up old Agfa Silettes and Brownies listed for £500
If I hadn't already learned enough lessons buying old cameras, I could easily be fooled into thinking that these various cameras were in perfect working order because some randomer listing it says so.
As film_man said, there are some fantastic, reputable shops selling various film cameras, that have been checked, come with warranties etc for the same/if not cheaper prices!
If I buy a camera/gear now from eBay etc, it'll be for a price that factors in a full CLA or something I can repair myself."