Should I continue a project someone else started?
Choosing a research project has always an element of gambling: the more challenging the project, the higher the risk. Meet personally with the potential supervisor and talk openly with him/her about your expectations and doubts. This way you will learn about the project things that you will never find out in publications or presentations. You will be able to see how enthusiastic and honest he is. Meet also with other members of the team and find out from them how it is to work on this or related projects with this supervisor. Ideally meet with the person who did the initial study. (If you start the project, you will probably spend more time with the other members of the team rather than with the supervisor.) Find out if someone recently dropped out and why. Finally, find out how "rigid" the initial topic is: is it possible to alter it in case things do not work out as initially planned.