I am 12 years old, I need some extra cash and it would need to be something that would make my mum willing to let me go out on my own since most jobs I could I get would include just that. I have looked on multiple websites and haven't yet found any promising ideas. I would love some advice.

Only thing you could get at that age is MAYBE walking a neighbors job, weeding their shrubs or garden, maybe helping them clean up the garage and take out trash. Unlikely these days to even mow the grass due to liability problems. The only business you could work at your parents would have to own. Due to age and very limited skills, and liability if you got injured.. there really won't be many options.

Sadly there aren't many positions for 12 year old kids. Most jobs require that you be at least 16, and even those are few and far between. Some allow 14 year olds to work, but again, few and far between.

At 12 your options are limited, but there are still things you can do. Babysitting, dog walking, lawn mowing, driveway shoveling, paper route, are the most common ones.