How can I send a prospective client an estimate?

From the "Manage" tab, click "Add New Client or Team Member". Enter in the email address (just the email address — don't use the "John Doe john@gmail.com"

Your prospective client will click the link we sent them to activate their account, and they'll be able to see the estimate you've laid out. Clients can, by default, add new requirements for you to estimate —  however, they're always unable to assign an estimate or price to anything.