Save Money : It's easy to see how free worksheets can save you money. If you want, you can skip buying math books and just use worksheets that you get for free on the internet. All you need to do is use a "scope and sequence" book that tells you what your child needs to be doing in math by age and grade. This book is essential when you homeschool.
There are other sources for worksheets also. You can find many public schools and private schools which will provide free worksheets for you if you buy textbooks from the school.
Remember to select worksheets that are the right level difficulty for your child. Get something too hard, and your child will become discouraged. Make it too easy, and they won't learn much.
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.