Payment for time spent on training

I may be taking a side hustle (self-employed). Before any projects is commissioned, all freelancers will need to go through a few training sessions with the client to learn to use their proprietary tools. The client will pay for the time spent by freelancers on the training but participation in training does not guarantee jobs. This means that as a freelancer, I may go through the training with the client but never get any projects (i.e., no income from doing projects for them). Do I need to declare the money received from taking part in the training (again, client is paying for freelancers' time spent on taking prat in the training, not for doing actual projects for them)?

Hi I,
You will  need to declare this income.
Thank you.