Yes, it is profitable to buy an expired domain but ensure that it has good page rankings. Aged domain name with good visitors ratio gets ranked soon.Whereas for New domain name, it takes time to get popular.So it is better to go for old domains with high PR
. You can check the domain name age using the site WhoisXY.com
.Domain age can be calculated using creation and expiration date of a domain. You can also know more details of old registrar here.