To add to the sensible comments already made …
It was Marcel Grossmann’s father who knew Friedrich Haller, the director of the Federal Office of Intellectual Property, and who suggested Einstein to him in April 1901.
There’s actually a reasonably significant period - April 1901 to June 1902 - between Grossmann telling Einstein about the possibility and him actually getting the job. While he continued to - unsuccessfully - apply for academic assistantships during this time and that was always his preferred employment, his immediate response to Grossmann was along the lines of that it sounds like a wonderful opportunity. The patent office then remains his consistent secondbest hope until he gets in, with the various schoolteaching and tutoring jobs he takes on in the interim only temporary stopgaps.
There were about another dozen Technical Experts in the Bern office at the time he joined. While I don’t know of any detailed investigation of their typical background, it’s clear that the norm was to have a background in engineering. I’d expect that most of them would have had a degree in the subject. Haller fairly blatently biased the job requirements of the particular position Einstein applied for towards him; employing someone whose only qualification was a degree in physics was unusual, but could be justified. There was also an expectation that he’d have to bring his knowledge of mechanical engineering up to speed. While it can’t really be proved (see below), the reasonable assumption is that, in practice, most of his work actually centred on electrical devices. Aside from his degree, he had some familiarity with the area because of his family’s firm.
His starting salary was 3,500 francs a year. This went up to 3,900 francs when the appointment was made permanent in September 1904. Then when he was promoted to Technical Expert II Class in April 1906 it went up again to 4,500 francs.
As comparisons, that starting salary was about double what he’d have been getting in the assistantships he wanted and when he resigned in 1909 it was for an Extraordinarius job in Zurich that was also paying 4,500 francs a year. And this was only after he’d pointed out that the proposed salary would be significantly less than what he was already getting.
As for whether any of this was livable on, at least one friend warned him that he wouldn’t manage in Bern on the starting salary. But it could be added to by out-of-hours tutoring and lecturing. It wasn’t always easy, but Albert and Mileva did manage to make ends meet in the city.
As to whether Einstein enjoyed the job once he got it, opinions differ. There are references in his and Mileva’s letters from the period (but particularly her’s) about how dull he finds the office and how it takes up all his time. One also finds occasional mentions of how he’s started looking for other non-academic jobs. Or complaints about what they’re paying him.
Yet he often made remarks about how the job was interesting, at the time and later. He even at various times recommended to his friends Conrad Habicht and Michele Besso that they apply to join. Besso did so and became a Technical Expert II Class; he had trained as a mechical engineer and had additional experience in industry. That appointment then has the non-trivial consequence that Besso’s there as a physics sounding board at the Cafe Europa downstrairs from their office in the evenings after work in 1905.
There’s thus been a notable recent trend to reassess the patent office job in a more positive light: see, for instance, Foelsing’s Albert Einstein: Eine Biographie (1993; in English, Penguin, 1998) and Galison’s Einstein’s Clocks, Poincare’s Maps (Sceptre, 1993).
We’ll almost certainly never know. The certificates or whatever issued to applicants weren’t signed by the Technical Expert and the internal paperwork was all routinely destroyed after 18 years.
There are a couple of cases where we do know what his recommendation was, but only because matters went to court. These instances are summarised by Galison (p249-51) and seem pretty dull affairs.
(Which, of course, all undermines the UL-factoid that Einstein awarded the patent on Toblerone chocolate.)