Your friend is a guy called SLA.
Service Level Agreement
You set how heavy the lash is for the amount of money the client is willing to pay. Doesn't matter the job.
- Low pay - SLA of 5 business days
- High pay - SLA of 4 hours
Some office guy exploded his desktop? You got a week to fix.
Some very important server went down because the maid pulled the cord midday? It's still a week, unless they hire premium SLA.
At least with SLAs, if you're getting called at 2a.m. if for someone that's worth it.
It's up to you really. Most of the stress comes from dealing with customers and managers, they are usually technologically ignorant and proportionally arrogant. Dealing with computers is the easy part.
You will only work after hours if you offer very short SLAs, this might be a dealbreaker for some clients, but you're the boss.
Things that will make your life easier:
- preventive maintenance, fix before it breaks
- monitoring, fix before they notice
- alerts, know before they know
As I said, even if you detect a huge problem and have to spend the night solving it, that is 10x less stressful than having to fix a simple email server with the client breathing down your neck. So keep tabs on your resources and monitor stuff. Let the computer tell you when it's going through hard times before it reaches a crisis.
On top of that, it's awesome if the client calls you at 2am and you're already up, fixing whatever it is and just saying 'Mail server down? I'm on it already, don't worry'
While you're working, make sure that you're doing whatever you can to prevent having to work other times. Like automating parts of your work or doing general prevention routines.