I think like many replies would tell you, the safest and easiest way to earn is through bounties. I say that because it would only take months, about one to three months at a time. Also, the tasks you have to do and commit to is not that hard, so the time you need to spend in doing them would not be so long as well, thus, it's not time consuming. That tandem of being easy and not time consuming is a good combination, coupled with the fact that if a project is a success, you get to earn in the max potential you can get. The downside, however, is the fact that there are many projects coming out day in and day out, therefore, you need to actually be thorough with checking which projects you join.