The first things I would check are the domain authority of the old website (assuming that it is still live and there is content behind the domain?) and also the domain health to make sure that it isn't blacklisted. Presumable the old website has a good DA and so you want to carry that link juice? From our experience with 301s, this should serve to carry that link juice on the condition that you continue to host +/ serve the old website.
A free tool for this is mxtoolbox.com which is pretty good but I am sure there are others available!
