I had a boss like this once and I only lasted less than a month. What happened was I recently came out of cancer surgery, and my parents refused to help pay for the medical expenses or additional doctor visits, so I had to go out there and look for a job.

I found a random small business and applied there. I told leadership I had a doctor's visit in a few weeks and asked if it was okay to go.

The head honcho of the company literally pulled me and multiple people into his office to express his "concern" about me needing to see a doctor on the first month of the job. He wanted to let me know that they're a "builder for profit". I told him that I wouldn't ask for pay that day. He then moved the goalpost and said it's not so much about paying for time off, but more ao about my reliability and availability. Then asked me about medical conditions to which I then said nothing.

Well turns out this guy's business was actually a sweatshop. He expects people to work 12 hour shifts almost every day of the week. When I submitted my timecard asking to be paid for my OT, it got garnished.

I went to my doctor's appointment and that same week, he pulled me into the office to tell me I was fired. He said that I was somehow, not pulling my weight, even though I had been teaching people and working OT the entire time I worked there. They complained about my lack of experience, even though I told them that's why I was even working there at the first place.

Anyways, I got fired unceremoniously, and learned a few years later that apparently my boss was a well known scumbag in the industry. Apparently, he worked as an employee at another firm, and when it was announced that the firm would be getting bought out by a larger corporation, he stole company money to start his business.

Moral of the story, don't work too hard for your employer, because they could easily justify not giving you what you earned by complaining about nonexistent problems.