Pros:
He would do all the maintenance, even if something wasn't broken he'd probably try to redesign it to make it better.
Would stay in his room so you'd hardly have to interact with him.
Takes quick showers so he wouldn't hog the bathroom.
If you're in college he'd totally help you with your tests/projects.
Would remind you if you're late for something or had planned to do something special that day.
Good with tech so if your phone or computer is buggy he'd fix it, or even build a new computer for you.
He won't eat the last piece of pizza, or the ice cream you left in the freezer for a special occasion.
Cons:
Very pushy, doesn't realize what your doing could possibly be more important then what he's doing.
He probably hoards old computer parts and scrap metal for his projects. If his room would get too messy he'd store some in your room.
Would steal stuff from you for his projects.
He'd borrow stuff and it'd be a long time before you'd get it back.
He's arrogant and thinks he's better than you.
Would get very upset if you invited friends over and didn't tell him beforehand.
Very awkward when the conversations haven't been pre-rehearsed in his mind.
All of his emotions channel into 'Angry and snappy'
Hardly sleeps so you could hear him pacing around or working at 3am.
Would ask you to turn the tv off as soon as you turn it on.
Very judging, and will make you feel bad about how you look or how your room looks, even if he does it unintentionally.
Is wanted by law enforcement.