Q: I know a book has to be in standard manuscript format for editing, but can I send sample chapters to an agent in single-spacing, to save paper?
A: I can understand your confusion over standard manuscript format, but editors did not create it, publishers did. A book is considered a manuscript until it is redesigned to be ready for publication. All manuscripts—and excerpts sent to agents or publishers—should be in standard manuscript format. The only exception would be when the author plans to self-publish, in which case agents and publishers will not be involved.
Self Publishing Advisor 