mreik,
I only bring up the bench option because it was suggested to me by a long-time and often-on-a-budget bodybuilder. He guesses a good Olympic bench would survive a dump of 500+ lbs (probably more than I will ever squat, and certainly more than I will squat for reps). And no, a spotter is out. No local buds, and my wife is a 130lb semi-invalid. One of the reasons I am training so hard is so that I can carry her up and down the stairs after she has knee surgery. I even have a lift for that: put a loaded barbell in my hands/over my shoulder and walk up/down the stairs. When I can do this 20 reps with her bodyweight I will be confident. Reason I chose 20 reps is because when the surgery happens, endurance/recovery is crucial. What I will need to do is move her up/down stairs once, but many times a day. This will go on for many weeks. If I can do this 20 times, then doing it 1 time several times per day should not be an issue. So far, I can make it up and down the stairs with her bodyweight only 3x. Needless to say, this is a GREAT exercise for the quads. BTW: 13 ft of stairs. Wife BW approx 135#.