THQ's Online Pass is a single-use code that is included for free in all new copies of games sporting the "feature." Users who do not have access to a free code--whether it be from rental or purchasing the game second-hand--can purchase an online pass for $10. EA has executed a similar program to sway gamers to purchase new copies of its titles.
According to THQ--via Shacknews parent company GameFly--users who do not have an online pass will still be able to play Homefront's online component; however, the experience is limited. Users will have access to all multiplayer maps but can only progress to a maximum level of 5 out of the full experience's 75 levels.
Users can continue to play the game online without an online pass for as long as they choose but will not be able to progress past the capped level. The single-player portion of Homefront is unaffected by online pass status.
http://www.shacknews.com/onearticle.x/67030