Apple iPhones and their apps work extremely well and many people will not consider getting anything else than an Apple product. While you can get a "free" phone through a phone plan, you will generally end up saving a lot more for it in the long run if you buy an unlocked phone outside of a phone plan. There are no deals to be had with new iPhones because Apple tightly controls product pricing. Like cars, it is always cheaper to buy a used phone and there are many companies that offer refurbished phones. If you like living dangerously, you can also look to the classified ads (like Kijiji).
Apple continues to sell older generation new phones but only a few generations back. If you can't afford the latest iPhone, even the oldest generation iPhone that Apple still offers will work just fine. If you're just going to use an iPhone as a phone, the cheapest version (ie, lowest storage offering like 16 GB) will be adequate. I would get the next larger option (ie, 32 GB or 64 GB) to ensure that you have enough room for apps, music, and photos. Not having enough storage will mean that you will have to be very careful with how much music and photos can keep.