Homeschool worksheets fortunately will not over-tax your budget. There are many places where you can get them at extremely low costs. In fact, several websites offer printable worksheets for free.
Review subtraction of 2 numbers whose sums would be 18 or less
It is amazing the difference in effort you will get from worksheet to worksheet. Granted the amount of effort may vary immensely from year to year depending on the group of students you have.
However, caution must be taken into account when review is repeatedly covered in your classroom. You do not want your students to become bored or frustrated with the repetition.