Characters from singleplayer to multiplayer

Can I get my singleplayer characters to multiplayer?

Nope.

Characters are serverside saved in multiplayer and singleplayer is clientbased.
Otherwise you could cheat the Sh*t out of the game in multiplayer.
But the server are quite active wich gives you a bit of a new experience when you lvl a new char there.
And the auction house can help a litle for gearing.