I suggest you to discover much, but after all these also they don't pay anything for us.
well most of this project are really scam but some after bounty campaign and they pays you, it will be very hard to list it's token on exchange.. although some may succeed to list but the price will be too small which even if you sell nothing to gain out from it. so i advise you to make sure you chose the right project before participating them. now there are bounty that is currently runing which can earn good income like yocoin, hussy.io, eloncity, oax most of them are signature for newbies so you can rush and participate on before it gets late.