For those who want the larger iPhone with the dual cameras, the base iPhone 7 Plus model is priced at $599. Note that since refurbished models are dependent on people returning them, them being in stock isn’t always a guarantee so you might want to move fast if you see a particular model that you like.
In terms of reliability, typically manufacturers who sell refurbished models will swap out parts that are old/not working properly for new ones. They also make sure that the whole device is working in good condition, so in reality while it might have been pre-owned, it has been cleaned up a bit and for the most part it should feel like new.
If you don’t mind refurbished handsets, then you’ll want to head on over to Apple’s website to see what else they are offering.