The second issue is that someone responsible for ordering food part time isn't going to do it as well as someone who's concerned with nothing else. It's specialization of labor.
If I had a great candidate for admin/manager, maybe I'd consider it, but I could easily see getting to 20-30 employees before doing so.
If you're stuck hiring them on your own (i.e. not part of a big company that has its own infra for hiring and training staff employees), several of my buddies who have started smaller companies swear by temp agencies. Quickly scan a few resumes, do a couple of chats, and then bring them onboard for a few weeks or a month in a try-before-you-buy role.
Also, if your admin does not _remove_ stress from your life, they're doing it wrong. Having had both decent and great admins, I can say that a great admin is an incredible enabler. Need your schedule to always have a three hour block of uninterrupted work time? Hate responding to urgent-but-unimportant crises that people always email you about? A professional, organized, and utterly ruthless admin is net positive w.r.t. your time and stress far more than they will ever be paid.