Walls and Ceilings - Building a small non-bearing wall

I am interested in creating a small bedroom in the corner of my apartment (5th floor) living room. I will use the two existing corner walls and put up two additional walls to complete the bedroom. (This is a very small bedroom for a baby-- like seven feet by six feet). I have never done anything like this before, but I am ambitious enough to give it a try.

I plan to beuild a wood frame and then dry-wall it.

Can anybody send me a rough estimate on how much the materials (2x4's, dry-wall sheets) will cost?

Also, how do i locate my ceiling and floor joists? Is it enough to anchor it just into the floor (i am considering not having it go all the way to the ceiling, to allow for ventihalation)?

I am not an expert so remember that if I use the wrong terminology.

First you have to figure out the length of the walls.

Such as 5 by 5 feet?
Now just call a hardware store, such as lowes.

Around here a 2x4 (un pressure treated since it is inside)
is about $3, maybe a little less.

Now just divide you wall lengths totals by about 18", stud spacing from center.

5 feet multiplied by 12 inches is 60 inches, so about 3 studs per wall, not including any door framing.

So a 5 x 5 room would need about 7 studs for the frames but you will want to figure out your doorway width and whether or not you will have a door on it. If you are going to install a door then you will probably want to double the studs around the door frame.

You really should get a piece of grid paper and design a layout.
1 foot for each square. Now you can figure out the stud placement and doorway. This will give you a final stud count.

Now you need to put 2x4 for a footer and header.

this will give you a wall frame like
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You do all these laying on the floor and then lift the frame.

Since this is an addition and is not a load bearing wall or anything you CAN get away with just designing it the way you want and forgetting the standards. I am going to be yelled at for that.

Find studs in the existing walls, just tap until it sounds solid, then drive a small nail to be sure it is a stud. Be careful not to go into a wire LOL.

Attach with nails or screws to the floor and existing walls. If it goes to the ceiling then attach there also.

Now just purchase wallboard and screw it to the studs.
Tape and Plaster the seems and paint.
Done. Except for clean up.

This would cost me about $100, maybe a little more with screws and extras.

Michael