Basement Heating: Ceiling vs. Floor

About how much per square feet does it typically cost to finish a basement if I do it myself? If I hire a contractor? The basement would have 1 bedroom, 1 family room and one bathroom (about 1000 sq feet).

Here is my dilemma. I have a basement with a concrete base. the entire floor was covered in wood subflooring, with many layers of linoleum, and carpet. I recently demo'd the kitchen and layed a 2nd layer of concrete to even out the base, then tiled it. although i think this is ultimately the best method, it took me an entire day, 40 bags of concrete and a sore back to get it done. it is much cleaner as a result, but now, in the winter months, the floor does get quite cold. as i began demo'ing the remainder of the basement, a portion of the wood subfloor (same floor as in kitchen, even more layers of linoleum..) was rotted away, so i tore it out. as time is an issue here, and the cost for a contractor to concrete the space is out of budget, I will install a new wood subfloor to match existing, and recarpet. the current subfloor is approx 6" off the concrete base. (this will all result in a sunken-in kitchen, about 6" lower than the remainder of the apt. i can live with this, i think!) my question - a lot of dirt, etc accumated in the floor under the wood, and im sure into my carpets over the years. is there a type of insulation that can be used in between the wood subfloor and the carpet/padding? its too late to get anything under the wood, i dont want to tear it all up just to re-lay it. what can i use? #2 - regarding walls and framing, ive installed new framing, with styrofoam type insulation in between joists, duct taped onto the wood just to seal it a bit more. (i did actually feel a diff here!) Is a vapor barrier necessary between the framing and the drywall? there has never been leaking into the walls from the block foundation. thx!