cool, so you hire one for 2x the the price of a full time one for 1 week per month. 12 weeks * 2x price < 52 weeks * 1x the price.
I've done this job for a 3-4 startups before. they can't afford a full time engineer, so they hire someone to work part-time to keep the lights on. its not a hard job and many engineers appreciate the consistent work and extra cash.