If you're a nurse in training this is the scumster's limited knowledge lowdown on mental health:
You will find it fairly easy to get jobs in in-patient settings- which, as you probably know, will offer lots of opportunities to work with interesting and challenging clients and a real chance to make a difference by being good at your job. The downside is that hospital mental health can be depressingly under funded and still, after all these years, feel unsafe for patients. Personally I have not yet been on a ward which truly feels like a safe place of refuge. Nursing staff on wards are paid less than those in the community, work comparatively longer shifts and often have less status.
This increasingly means that many mental health nurses covet and compete for the community jobs- in community mental health teams, home treatment teams, crisis resolution teams etc. These are harder to get because of the increased competetion and because these teams are multi-disciplinary so sometimes have fewer posts reserved specifically for nurses. Nurses are highly prized because they can give medication though.
There are also some roles in 24 hour care homes/residential homes etc. Suspect these would be quite badly paid though.
In short, I reckon you'd have no trouble finding a job, but might have to work up to a community role if that's what you're thinking of. I also think mental health nursing is crying out for people who are enthusiastic and committed, especially on the wards and it's great that you want to do it.