For most kids they cannot start working until they are at least 13 or 14 but if you want to get started before then there are a few jobs you can look into to gain some cash or pocket money.
Extra / Background Artist – This can be a long boring job especially for young children, however my daughters have done a few days and thoroughly enjoyed it, the pay isn’t bad either if you are registered with an agency. Many agencies all over the UK take on children for casting work, just do a search for casting agencies in your local area and you just submit your child details in order to get on the agency books.
Modelling – Paid modelling work is rare however they always need child models to promote clothing, school wear, toys, games and everything you see around you advertised with children on it. Similar to the extra work just take a headshot and full body image of your child ideally on a white background and search for local model agencies. Many of them are in big cities such as London or Manchester so it is ideal if you have good availability and can travel. A lot of the agencies now especially in casting have a stage school attached to them so if you enrol in the stage school it may give you an in for the agency.
Odd Jobs – Can you water plants for an elderly neighbour, are you old enough to babysit, can you deliver newspapers for your local shop. What about decluttering your room and doing a car boot sale of your old toys and games to raise some money?
Art – If you are really good at drawing why not make some lovely art work and try and sell them on art spaces online, even creating your own website to sell your work or on places like etsy (May need mum or dads help)
Youtuber – Have a special skill or a really engaging personality why not create some videos for youtube – Love Minecraft and want to show your creative side or want to show the world your favourite toys – There is a home for you on youtube, some kids have even become famous from youtube
Writing – Have a best seller in you or just want to write for enjoyment? You can become an author and self publish on amazon – Great achievement if you are young and you can make a few pounds.