Hulu reportedly will introduce a subscription plan as soon as May 24, which would cost $10 per month for access to anything older than the last five episodes of popular TV shows, according to the LA Times.

The subscription plan, dubbed Hulu Plus, would not affect those who regularly catch up with recent episodes of their favorite shows on Hulu. But anyone who wanted to watch episodes older than the latest five free (advertising-supported) episodes would have to pony up $10 per month, the report says.

There are some unknowns about Hulu's subscription plan, though. There are no details on whether the $10 subscription will let you watch an unlimited number of episodes from the site or if there would be some sort of metering in place. Also, it's unknown if advertising would be displayed during the back catalogue episodes.

The $10 price-tag of the Hulu Plus subscription is arguable as well. Over a year, it would equate to $120 for shows you could, in theory, watch on TV for free. For those who regularly follow only a couple of TV shows, it would make sore sense to purchase episodes from iTunes or buy the DVDs.

Hulu is the second most popular destination for Internet video after YouTube in the U.S., and is expected to generate over $100 million in advertising revenue in the first half of this year. Hulu is owned by News Corp, NBC Universal, and Walt Disney, and offers free-to-watch full episodes of popular TV shows such as Glee, Lost, or Saturday Night Live, among many others.

The $10 Hulu Plus monthly subscription plan is only the latest additional revenue idea for the company. Earlier this year, Hulu was rumoured to prepare an Apple iPad version of the service, but not further details emerged since.