In Oblivion I joined the DB and found their quests to be among the most fun. And I feel that in Skyrim they will be even better. But I want to roleplay a character that isn't evil, more like chaotic and neutral with good tendencies. What could be a good motive for such a character to join the DB?

He has a love of killing? >.>

He's a serial killer with a heart of gold?

Septims

Money and a placing little value on life.

There's really not a way to be good. Especially if the DB continue to be a Sithis cult. The best you can do is simply want the money.

Avenging angel-type?

Your mother's head told you to join for revenge?

that once you reach the top and weed out all the top members you plan to kill all the DB and restore peace to Skyrim? It's a means to an end!

Because of your Dark Passenger

You're embracing chaos. You're abandoning your own logic. Does someone deserve to live or die? Who cares! Some arbitrary fellow decided that he wants your target dead, and that's all that matters. Maybe this murder will be evil. Maybe it'll be good. You don't know, and that's awesome.

Your character tries to change the Dark Brotherhood from the inside. Emphasis on "tries".

Because the voices told you to.

Money perhaps. On some of my neutral characters I like to pretend that they are mercenaries that will take any job, whether it is rescuing villagers or an assassination.

Well i liked the join them to kill them all philosophy, it suit well a chaotic good character...good must be achieved at all cost.

I like to the gold they pay and some of the items you get. Plus I imagine you will be able to send out members to kill random people or ask them for help. Also Sithis demands it.

They promised you cookies.

Dexter FTW

Because you honestly believe that they are serving the "greater good" by assassinating criminals and other threats to society?

I am joining them to inflitrate and kill them all. Yes, I want to attempt to rid Skyrim of the DB.

What my character's motive to join the Dark Brotherhood is going to be similar to Batman's in Batman Begins. He's going to join the DB early on (in order to survive) and gain combat/stealth skills throughout his training. Once I've competed the DB I'll use these skills and become a good character.

That's kinda like saying I want to role-play as Santa Clause, but I need a good reason to paint eggs and hide them for the children....

I honestly can't think of any reason that would validate it in my mind, other than making a separate character to experience that part.

If that is not an option then the only thing I can come up with, is maybe your character got bopped a little too hard on the head during the last dragon fight and is suffering from temporary amnesia and happens to fall into cahoots with the DB while trying to discover their identity.

Because you need money and most of those people deserve to die anyway.

I don't think you can be a dark brotherhood assassin with good tendencies... you're living a life of murder for a cult that kills in the name of a rather dark daedric prince (sithis). Unless they have some sort of coercion to force you to do it, but that's not the brotherhood's style, you're there because you want to be. I think you'd have to be somewhat on the evil side of the alignment scale to even consider joining.

Neutral would be "I don't want others to bother me and I don't care what others do, I just want to be left to live my life as I see fit. I don't mind getting my hands dirty for something I want, but I don't necessarily want bad things to happen to people. I won't go out of my way to help people either unless there's something in it for me." Doesn't seem like the kind of person who would join a hitman cult. Unless they're have an odd fascination with murder...? I don't really know.

It seems like this person would be more at home as a thieves guild member. It's against their rules to kill, they're just after the loot. Maybe they can steal from the rich and give a little bit to the poor. That would fit a chaotic neutral with good tendencies. Can't think of a reason they would join the Dark Brotherhood though. They're a rather wicked bunch.

He could hold the belief that people the brotherhood are contracted to kill generally have it coming.

Alternatively, you could spin it as a "generally good" person being drawn into the webs of a dark cult. This adds a certain complexity to the morality game, since it assumes someone's morality isn't fixed, but constantly in flux.

I started Oblivion to pass the time before Skyrim and I found that my Nord Assassin joined the DB not because of gold or items or quests. (albeit they are all good)

He joined because he needed a safe place to go because my freelance killing got me into so much trouble with the authorities that I couldn't go anywhere without the guards hunting me across Cyrodiil.

Thankfully I made it to the Cheydinhal Sanctuary (which it really is for me this time) and now all I have to do is sneak past the Cheydinhal gate guards and I can go do as a please.

For someone trying to be "good" in the DB, I can really only imagine someone who believes they are doing the "right" thing by undertaking these quests. Or maybe this character has no other option? Maybe they desire to do "good", but have no other means of doing it.

OR perhaps the law did something to the character to instill hatred in them, so now they work for the DB to exact revenge, thus the character is doing "good" in their mind.