one last push for the extreme basic, of works for ya.... don't get all fustrated with various computer programs. just break out some paper and penicels/markers/pens. and go at it. rough things out your plans will change multi times. cut out some pieces of cardboard or paper, mark what it is, bed, couch, chair, etc.... to near size. and move stuff around.
figure approx 30" to 36" for walk ways. (measure width of doors, when doors are open ya walk through them. not overall size but just the area you walk through), measure distance from around bed, and dressers, around the kitchen for an island, etc..
the cardboard cut outs work out nicely, if you have something drawn up on graph paper say 6" per square, and trying to move a bed, couch, dresser or like to a bed room through a hallway and trying to get it to fit around corners. ya just put the cut out on the graph paper and push it around. same goes for washer/dryer, bathtub, etc...