If you will look at the Authors and Illustrators listed by us you will see a wide variety of fees and some are negotiable. School Visits are usually broken up into several sessions. It is wise to check with the author or illustrator about how many sessions they do in a day. It is customary to have a check for the agreed fees and travel expenses ready to give the author or illustrator when they come to make a school visit. Your school may have discretionary funds some of which could be budgeted for future school visits.
Many educators write grants to obtain funds to cover several school visits within the year.
To see a sample of state grant information click here. For instance application can be made for Grants for schools in Kentucky. Other educators hold book fairs every year and use the proceeds to help fund school visits. Preparation is always the key to success. Make sure the students are familiar with the published works of the Author or Illustrator.