older model iPhone (7 / 8) unlocked (Seven Oaks)

I know this is a reach but I'm hoping someone upgraded their iPhone a few years ago and still has their old iPhone 7 or 8 hanging out in a drawer. I would like to set it up for my 86 year old mom to try so I don't want to spend a lot getting the phone in case she hates it. She's currently using a cheap flip phone. She can't send or get texts and has to remember the number she wants to dial because the menu to get to the stored numbers is too difficult to reach. She complains all the time that it isn't loud enough. I think an iPhone would work for her because I could remove everything except the very basic functions. I can set it up with a no contract service for her to try. With a donated phone, if she hates it I'm only out the time I spent setting it up and $20ish bucks for the first month of service. Thanks!