What does it mean for a photographer to take a guest photo when taking a first-grade photo?

There is no need to spend extra money. The so-called guest photos are the photos of sample customers. Sample photos are usually taken by professional models and used for studio publicity. It says here that your children are in good condition and want to use your finished film to promote the studio (that is, the sample film that the studio showed you when you went to choose the style). I hope my answer is helpful to you.