In a major financial pinch and about to lose my apartment I was living in, I was invited to stay at an online friends place in Arkansas (small Apt on his property). It use to be a garage for working on cars a few years back and the owner at some point converted it to 2 apartments. The problems were evident when I first stepped foot into the place. Noticed excessive condensation on the windows (one small front window and one small window on the door) and also noticed the toilet tank excessively sweating and dripping on the floor. It only has 2 rooms and smelled very musty... had to pull up a carpet in the main living area as his wife tried to use a steam cleaner on it, but it never dried out and noticed lots of mold under it which I cleaned up with some bleach solution and also has what I believe to be black mold in the back room in a corner of a closet... also next to the sink on the wall above (and probably behind) and also outside the door that leads to a small crawl space between the 2 apartments where the hotwater heater is located. The whole place is concrete and I have no clue if there is any kind of insulation or anything within the walls or the ceiling. Beings it was cold we turned the (non standard) heater on which is run by natural gas (this is what it is, just an older model) http://www.nbmc.com/vanguard_images/v20.jpg . I turned it on low which only fires up one of those 3 elements and when I woke up this morning I noticed the back room floor (which he also pulled the carpet up from), looked damp and lifted up the 3 cat carries and there were 3 dry areas in the shape of the carriers... leading me to believe the moisture was coming from the air and not up from the floor. The 2 windows were horribly dripping with sweat and so bad there was a puddle in front of the door (inside of course) and a puddle on the wooden sill. Oh and one other thing... the front inside wall and ceiling were also sweating. He suggested using the electric oven (temporary) just for testing purposes as he said something about natural gas creating moisture or something like that and that the electric heat is a dry heat and should help with the humidity. Seemed to work for a bit, but then it got just way to hot and had to turn it off. Im not sure what if anything would really help me out here, as I need carpet put down, but with the condensation/humidity so bad... it would just lead to a wet and moldy carpet again. Was thinking about possibly trying some electric oil radiators to see what if anything they would do... and also talked with my buddy and he suggested these options... Strip off all the baseboards and clean the walls, ceiling and floor with borax to get rid of the mold... use some fans to help dry it up and then apply KILZ Masonry Waterproofing Paint (though aside from it helping with the mold, Im not sure what the waterproofing will do if the water isn't physically leaking into the house). Then from there once dry, paint everything with Zinsser Perma-White Mold and Mildew-Proof Interior Paint. As you can see... its a real mess and my head is spinning trying to figure it all out... its like, should I get a dehumidifier and keep using the ventless gas heater or is this whats creating the condensation/humidity and should I instead opt for the oil heaters and do all the cleanup and painting/sealing. Sure hope someone can help me out before I lose it mentally.