Your question is too vague and not immigration related.
automotive mechanic, electrician or photography/videography
In many countries, you can just set yourself up as an electrician and start trading next day. You will see that in the UK, most jobs are regulated and you need an accredited training
to be allowed to do them. Electrician is like that.
A lot of training is also required to become an automotive mechanic. Most people go through 3-year apprenticeship (they are 17 or 18 years old when they start
). These apprenticeship options are usually not available later in life.
Photo/Video... It's a dead business in the UK. You will struggle to find anyone who pays for that. It takes years to prove yourself and start getting clients. Most people I know who tried that field dropped after a few years where the spending on cameras and equipment was never paid back. When you spend £10'000 on equipment and you get 1 client paying £200 after 9 months doing marketing, you get the point.
But your question is really vague. It means you are the beginning for this line of thought. You need to explore with your partner and establish a career plan and projects for him. But it needs to be more focused than that.
All the best.