What type and how many characters can be used in a domain name?

You can incorporate the numbers 0-9 and letters A-Z in the domain name.  You may include hyphen(s) but your domain cannot begin or end with a hyphen. Spaces and underlines are not permitted.

.realtor™ - A domain name MUST be between 3-63 characters in length. 
.realestate - A domain name MUST be between 1-63 characters in length.