When I was last renting (in the UK) I changed my locks the day I moved in, then swapped them back to the original cylinders when I left. I thought it was pretty good practice not to have a door with an unknown number of previous tennants, cleaners, letting agents, landlords etc with access.
It never occurred to me not to change the locks. The minute I start paying rent, I always saw it as my home. Upon viewing the place, I make explicitly clear that I expect it to be cleaned and anything that's broken shall be fixed prior to my taking possession and that I will consider the contract null and void if it's not. I ensure this is written into the contract so that if it's not taken care of, the contract is n…
I've had applicants who insist on similar changes, and I'll decline their application every time. It sounds like you're a good guest, but without knowing anything more about someone, I take such behaviour as a big red flag.