Do I need a monitor and keyboard

I'm close to buying a used mini PC and I just realized I don't have a spare monitor, keyboard or mouse. My Windows PC has them, but I don't love unplugging everything every time. I think after the first install people just use it from another computer over the network, so I'd only need the screen and keyboard once.

Can I skip that part completely, or is it a bad idea for a first timer? If I do need them, is it worth buying a cheap used monitor and a basic wired keyboard, or should I borrow a TV and a keyboard from someone? Does a mouse matter if it's only the Linux text install? What would you do if you were starting again?