At work we have a 24/7 20min response time clause. If the phone for work emergency calls we are ready to help in 20 minutes at any time around the clock even on Sunday.
Why would you do anything else for your sysop/sysadmin?
You surely realize that no human being can be available 24/7 within 20 minutes. It's beyond slavery to expect that from any employee.
You need at least 10 sysop/sysadmin to achieve anything close to that SLA, with a sustainable rota. Contrary to the parent posters who believe it can be done with THE right guy.
With 3 people you can have a "follow the sun" rotation during business hours which takes care of the entire week, and I don't think you would need 7 more people for the weekend.
Not all 3 have to respond all the time. It's a rotating schedule for having the overnight phone and the weekend phone (during weekend nights the SLA is relaxed to 1 hour).
And keep in mind, 20 minute response doesn't mean you fix the problem in 20 minutes, it means you respond in 20 minutes to the callout.
I think you're victim of an easy-going startup culture.
You need at least 10 sysop/sysadmin to achieve anything close to that SLA, with a sustainable rota. Contrary to the parent posters who believe it can be done with THE right guy.