Well done Whitewave, lots of cats out there, and some old ones and black ones do struggle to find a new home (black cats are just a bit less popular).
Someone mentioned the 333 guideline, but things may differ. There are folk who take cats back to a rescue after a couple of days because it did or didn't do something, just a silly attitude. We cannot know that cat's back story, what sort of trauma it went through.
We've had nervy delicate souls, one spent the first few days behind the sofa (came out at night to eat a little), and another was terrified for several weeks (turned out she had an eye infection, couldn't actually see the new house and people very well). We also had a laid-back, confident ginger giant, when let out of the cage he looked at us, walked round the house twice, came back to the feeding area and wanted some lunch.
Our present chap was 14 when we took him on, that was nearly 3 years ago, and he's presently on the floor behind this chair as I type, he discovered a bit of floor that has a pipe feeding the radiator, so he lays on that. He likes sofa, chairs, but rarely a cat bed (he noticed that people don't use them, so obviously they're inferior). He's manic for food treats, so likes a bit of ham or cheese at lunchtime, and if there's a bit of raw meat or fish when dinner is getting prepped, he gets a little of that too.
Pet insurance is a nightmare area, something to consider as despite the expense, it can be be a godsend if you do get a chunky vet bill?! But shop around!
Jolly good luck!