Yup...My rear passenger floor is completely gone, but when you lift up the carpets you wouldn't know! It looks to all be there. Even looking underneath the car all you see is a sturdy looking floor.
And then you put some pressure on it and you can see the whole damn thing flex.
These old Mercedes certainly hide their rust very well. I just remind my rear passengers to not stomp their feet too hard, lest they end up damaging their shoes what with their soles dragging over the asphalt!
In all seriousness though: if you can't weld (I can't either), call some body shops. Have a quote done if the rest of the car is still good. Rotten floorboards are not necessarily the end of the road, nor does it have to be (too) costly to get it fixed. You could even check craigslist or something, see if some local welder is offering his services in the nights and weekends...
It's a floorboard; the welds don't have to be too pretty, as long as it has fresh metal and gets rustproofed!
If all else fails, you can do what this guy did with his car (I actually took this picture two days ago, while sitting at a stop light during my lunch break)
He had his seat propped up on wood. You can tell, as it was poking through the floor.
Oh, and this is the carpet!:
It was raining, too. Pretty sure his socks got wet...
