What happens with domain names that are placed on hold, when the owner has not paid the renewal fee for the name?
The registrar can offer a grace period to the owner of an expired domain name by putting it on hold. When the grace period ends, the name is dropped from the domain name database and is returned to the pool of available domain names. There are some domain name brokers, who search for expired domain names and buy them as soon as they are dropped. Since the process can be automated, you can expect to compete with software programs if you take this approach.