DON'T DO IT! I think you will find it a complete waste of time and money. European airlines are unlikely to be that impressed with the time you will get. Sorry and all that, but that is the way it is.
As other posters have suggested, the F.I. route is probably a better investment. Or parachute flying. You probably won't earn much with this type of flying and possibly nothing at all in the winter but you could get some non-flying work to cover the winter months while you gain experience over a couple of summer seasons. Others have done it (including me.) Or go somewhere where the weather isn't such an issue and the flying hours will come quicker. In any case, you will learn to fly, and you will have some fun!
Also, may I suggest you read 'Squawk 7700' by Peter Buffington. His experiences of trying to earn a living flying in the States. There are plenty of references to exactly those types of schemes you are considering and also the heart breaking reality for many pilots at the bottom of the industry. I don't want to put you off the career altogether but if it takes the rose-tint off your glasses and makes you see the brochures and websites for these 'opportunities' (sic) then so much the better.
If you need 50 hours then perhaps some hours building in the States (use the time to get some night flying in) or perhaps a share in a light aircraft (the LAA types are fairly cheap to operate and you can always sell the share afterwards)
Best of luck, anyway!