Quote: "Do I need that a used Mac be able of emulating iPhone?"
Yes, any of the Mac family from Apple.
You can also use it connected directly to any iOS device to install and test directly on the device.
You will definitely need a Mac if you want to publish for Macs (it's in the Mac Developer License agreement). And it makes it easier to publish for iOS (I'm not sure of other methods for doing it, but the iOS Developer License agreement doesn't require that it be done on a Mac).
I use a Mac Mini. It generally costs less and you can put any monitor, keyboard, mouse you want on it (not tied to just the ones Apple sells). If you happen to have the peripherals, the Mac Mini is definitely the least cost way.
Cheers,
Ancient Lady
AGK Community Tester