How much does it cost to tear down a wall?

This depends on if it is a load bearing wall or not. If it is load bearing, it supports the roof or higher story and cannot simply be taken out. Jacks must be installed before the wall is removed, and something else must be built in its place to handle the weight. If you don't do this you will regret it. With all the proper equipment this can be expensive, and depends on the job. If it is not a load bearing wall, not nearly as much. Removing a non-load bearing wall is a matter of removing any mechanical fixtures (lights/outlets/plumbing/heating), knocking the wall down, and then patching the hole where the wall itself was to blend the now joined room. It it is just a wall, I'd say around $20 for a sledge + paint & plaster. Please check that it isn't load bearing first, though. If you succeed in knocking out a load beaing wall your house may collapse. At the minimum you will do severe damage to the now bearing walls as the house settles into its new position.