There is a misconception out there about the word saint. Whenever the word is used in Scripture, it refers to something or someone being consecrated or set apart to be used by God. That's why Paul called the Christians at Philippi saints. They were ordinary Christians like you and me. Acts 16 gives background on some of these people.
A merchant woman named Lydia sold purple dye which was quite rare. She came to Christ through Paul's ministry; therefore, she is deemed a saint in Philippians 1.1 (see Acts 16.14). A fortunetelling, demon possessed slave girl came to Christ in Philippi; therefore, she is deemed a saint in Philippians 1.1 (see Acts 16.16-18). A warden at the prison that held Paul was about to kill himself because he thought he lost all of his prisoners during an earthquake (see Acts 16.25-33). Paul stopped him and led him and his family to Christ; therefore, they are deemed saints in Philippians 1.1.
Anyone who is a Christian is set apart by God for His purpose. That makes them saints. I've attained sainthood. What about you?