Hi op, I don't know how old you are or if you have kids, but I'm one of those 'zero waste' environmentalists, and have managed to work around tight income by changing my mindset.
I'm not single or childless, but if I was, I would look for a job with a live-in arrangement. They are out there and I would probably do something like that for a bit to top up my savings. I would rent out my place for additional income and come back to my life when I'd saved enough.
Also, right now I grow some of my own food on a balcony plus forage (blackberries and apples!) and preserve.
I hardly buy any food. I go skipping with some other like-minded friends of mine. Skipping is finding good edible food that shops and restaurants throw away. There's a lot of it! And finding a group who can show you how to do it it's not too scary. Just yesterday I filled my fridge with perfect apples, oranges, bread, yoghurt salad, minced meat etc. All in perfect condition, but had been thrown away. Mentally it's a challenge to get started, but ince you go and see what you can come home with, it becomes a no-brainer.
You can also get nearly anything you need for free. My whole 3 bed home is furnished with stuff from free cycle. I enjoy knowing I'm actively reducing the amount of waste in this world, but I'm definitely enjoying financial benefits from it too.
Just a thought. Not for everyone.. I understand.