give some idea of compensation (salary range + equity). If the client is profitable, talk about that. If you don't get any qualified people after a bit, either reduce what you are asking for, or up your offer.

Differentiate between skills the candidate needs and skills that would be nice but could be learned on the job. Give some examples of tasks that the person would do.

Consider splitting up the broad responsibilities into discrete entities, or several jack of all trades. Remember if you have one guy who does everything, that guy quits/dies, there is no guarantee of any documentation having been written.

Alternatively, consider hiring a (paid) intern or junior engineer so that your big hire can focus on the big issues.