This is the reality, don't expect every code base is clean and well organized. I have come across the same situation for a couple of times in my career. I felt disappointed at the beginning, I wondered how high-paid engineers could write such shitty code, but quickly I found it's actually a very challenging job. To understand the code base was like playing puzzle games with debugging tools. I had invented tools with some new stuff I just learnt to trace and visualized the program, or wrote scripts to clean up the code. Eventually I became the owner of these projects, and refactor the hell out of it.
It's a known issue that latest version of Mac OS has problem to connect to external 4k monitors. I did not experience kernel panics, but lagging on display, high memory and cpu usage on the windowserver daemon.
It really depends on what kind of apartment you live in. for a luxury one, it can easily burn you 3k+ for a 1b1b, however, if you are ok with sharing space with the landlord and other roommates, for one bedroom, it's usually around 800 including utilities and internet in south bay. And you probably don't need to pay for food or gym, most big companies provide that.
You skill will not rot if the code base is old and bad, your attitude does. It's just not your conform zone, it's ok to avoid it, but you will learn a lot if you don't. Spend some time to understand the business logic of the legacy code by doing code review, debugging...etc. and see if you can improve it by back porting the new technology, there's always room for that.
a bit off topic. NVIDIA driver for mac is kind of suck. the bug, which showing a transparent window whenever you try to open an epub file with ibook.app, is been there for a very long time, and still no fix yet.