Lena’s parents are sick and don’t make enough money to get by themselves, and definitely not enough to send her money. So she dropped out of college to earn money to survive herself and help them out. Ian’s parents don’t have similar problems, and from what he told in the latest chapter, it sounds like his father is pretty well off and having a successfull career (surprise appearance as an acquaintance of Seymour in the future, maybe?) so there’s no reason for Ian to do the same. It’s not really comparable, and we don’t know whether Ian would have done the same in that situation. Lena also has a good relationship to her stepfather, who is the one who originally needed help, so that’s a part of the equation too. And while Ian can ask for more money from his dad, Lena can also stop sending money to her parents, so that choice is pretty symmetrical within their different context.
It’s also true that Lena’s got two jobs, while Ian’s only got one, but his job is likely to be more hours. And with Ian having the book writing and the MMA as side projects, and Lena having the modelling and the music career, I don’t agree that Ian’s life is particularly more relaxing. So I still don’t see what would make Ian a "useless leach".
And the complaining? I don’t see that big a difference between them there either. They handle it a bit differently, that’s true, but compared to other characters like Alison, Wade, Cindy and Louise, I don’t think Ian stands out in any way.