What to do with old Apple technology?If on a new there is no money!

Hello, my name is Dima I from Russia would like to ask a question!I am 29 years old and I am raising my son alone and I really like Apple and iPhone 5s was my dream!Since prices for Apple products my financial position is not affordable and iPhone 5s in the thrift shop I was able to buy only in 2017 !Do you want to know after iOs update when it stops updating like my iPhone 3 and iPad 2 What to do with them???If for example on iPhone would 8 or's money there is no!

Can there is program 3 product Apple outdated're giving up,and you for example one a new???