Good question and this will be the biggest challenge. The answer is equity. But be careful before giving too much equity too easy away. You should have a big pipeline of candidates and know exactly what you expect from whom and how much you are willing to give away and on what conditions. At the beginning some might join your venture full-time, some not. Latter ones are easy to get but eventually it might be hard to get them out of the current jobs if the prospects are not to positive or let's say the first round is rather small.

Once in later funding stages (A, B) you have much better financial power and thus, you'll update or upgrade your senior management team anyway.