Jetstream rating
F Fred has a point.
I always say to myself, what is the worst scenario. And that is you pay £15k for a J41 rating and the business folds/base closes/cutbacks and you are laid off etc. That can and does happen. I have been laid off and/or made redundant/company gone bust on six separate occasions. Ok I have been unlucky, but there you go. So you are sitting there (minus £15k) with no job, but with a J41 rating. Not good.
However, if you invest more in say a B737 or an A320 rating and you get dumped put of work, yes you will be minus £25k, but you have a very good chance of getting more work (and better paid than a J41). It may not be in your favourite location, but you will get work within Europe.
I would be very careful investing hard earned/borrowed cash on a turboprop rating. I did it once myself and it was a big mistake. I swore I would never buy a rating again. But a couple of years later I bought a B737 rating with the promise/possibility of work. A short time later the company went bust - but I got work straight away as I was type-rated and current. Two valuable commodities in this business. After three years my rating loan was paid off and after learning a great deal from my colleagues, I was able to get my first jet command. End of story.
However, I wish you good luck, but thought I would pass on my own experiences to you.