Cbren
For starters, get as many medical background as you can to gain the best chances.
But remember, rearcrew is hired most of the times after the age of..............35.
All to do with life experience and .................common sense in the way more mature people think............exceptions can be made.
Young people on the job who will take more risk and danger to themselves is a factor that companies don't want and don't tolerate.
The first criteria as rearcrew will always be.....own safety first.....crew....AC.
At your age you will have the time on your side to do the background training which is needed, like Paramedic which will be more and more the entry level in the SAR world for rearcrew.
Good luck