Hi
In some countries (including the US), Apple offers a trade-in program for iPhone. This offers instant in-store credit towards the cost of a new iPhone (if trading in at an Apple Store) or a Gift Card (if trading in via mail) when trading in an eligible iPhone.
In the US, for example, the estimated trade-in value of an iPhone 5s is currently $95 (terms apply):
http://www.apple.com/iphone/trade-up/
You may also find the iPhone Upgrade Program (also available in selected countries) of interest:
http://www.apple.com/shop/iphone/iphone-upgrade-program
Another option is to sell your iPhone 5s privately and put the proceeds towards your new purchase. If doing so, be sure to follow the steps here:
What to do before selling or giving away your iPhone, iPad, or iPod touch - Apple Support
The only way to get a definitive trade in value on any iPhone is to take it in to Apple and let them evaluate it. Any price you get from the web site (e.g. http://www.apple.com/iphone/trade-up/) is an estimate, subject to final approval upon physical examination of the trade in device.
Nobody here in these user communities speaks for Apple, so nobody here can give you any estimate other than the basic one obtainable from the web site. Your upgrade price will be the difference between the retail price of your choice of new phone (also available on Apple's web site) less whatever trade in value your old phone ends up being worth.
How much does it cost to upgrade my iPhone 5s to and 6s or 7?
