@piponfishing@sunbeam.city [Part 2]

Fertility: you may quickly find that the soil you use is getting poor after just one or two seasons. Many urban gardeners go for synthetic fertilizer but really, you may as well buy store veggies at that point. #wormcomposting is a brilliant solution, as you already thought, and I suggest to also ask neighbors and friends for their organic waste, maybe compensating with a dinner from time to time. It's a nice way to bond =)
Don't go for sustainability. Doesn't work here. You don't want systems that may go on indefinitely, you want to gather as much resources from the outside (other people waste) and convert it into useful things. This is way better than going self-sufficient or sustainable in urban areas, both for you, your production and the environment.

Mushrooms: for pleurotus main things are humidity and fae (fresh air exchange). You can start by buying the pre-inoculated small strawbales, and go on from there. You can have them in deep shade, a simple compact fluorescent light for 3-4 hours a day is enough to trigger the growth (they will be weaker in vitamin D and other nutrients, but it's a good tradeoff). They surely require more effort and knowledge, but boy they are fun.

Last thing, maybe consider some guerrilla gardening. If there are some abandoned place, just go and plant a fruit tree, and some other low maintenance stuff, and go collect them when the season is there. In open land there is almost no work involved, just some pruning from time to time.