Can't get in to his own house?

Maybe he lives on his own? Did they ever say how old he was or whether or not he was still in high school?

Were you guys too focused on Johnny Depp to follow the storyline? hehehehehe

Getting into the house wasn't really Jim's concern. Jim wanted money to buy a new van. Even though his parents are wealthy, they don't buy anything for him, so he wanted to get money from the vault of his own home. The vault is insured, so if it were to be robbed, the insurers would pay them back the money -- so it's like getting a new van for free.

Jim just wanted to be able to blame the break-in on someone, just in case his plan [to steal money] failed -- which is exactly what happened. He even mentioned that his dad would have his own son arrested for going after their vault.

In an earlier scene, Kim was locked out of her house. Edward unlocked the door with ease. Jim was there too and witnessed this and he wanted to take advantage of Edward for that very purpose (lock-picking, plus Edward being naive). Jim lies to Edward saying someone stole Jim's money and he wanted Edward to break into "that person's" home to get it back, thinking Edward could get around the alarm mechanism, but couldn't. Edward is then arrested, but released because a psychiatrist states Edward has an under-developed sense of "right and wrong" because he has had no interaction with society for most of his life. Edward later reveals to Kim that he knew about Jim's plan the whole time, and only did it for Kim.