How long to wait after getting a first cat?

[TheSecondMrsAshwell]

So I am planning to move and once I'm settled, I planned to adopt a pair of cats. However, a cousin of mine is looking to rehome her 7 year old cat; she's allergic to him and he no longer gets the attention he needs from the children (he was bought for them in the first place). I'll be meeting him next week.

Apparently, he is cat friendly (he has mates in for a spot of sofa surfing) and is generally very good natured. So I was thinking of getting him a companion cat. But as I haven't even got him yet, I need advice on how long to wait before starting to look for another cat? What if the new cat doesn't get on with mine? Can I return it to the rescue and try with someone else?

I'm looking a way ahead so as to do this properly.

The best hope for getting two unrelated cats to coexist peacefully would be to rehome them at the same time such that neither one is "on home territory" abd feeling they own the place when the other arrives, but thar they are both getting used to the new place and the existence of each other at the same time.

Yes I second that, get them together, gives them an even footing. Unrelated cats are rarely friends (although it does happen), but will exist happily alongside each other once they've established who's boss.

Cats are naturally solitary and don't need or want a "companion"

cats 'naturally' live in feral colonies. They learn to live with each other.

Mutual move to new territory sounds good.
I imagine they start in different parts of house never meeting each other but going into each other's territory (leaving smells and hearing each other). When no longer freaked out by new place/smells, they might be allowed 2 second sights of each other. Slowly build up to longer views. Not allowed to physically meet until they can handle the viewing without obvious distress.

Short short spells of meeting in person slowly building to longer.

Is what I'd think to try.

I was just going to have one cat but my cat kept going out and trying to make friends with every cat she met and got beaten up by some of them much to her chagrin so I got her a kitten. Same sex. Big cat used to look very anxious all the time before kitten came along.
Both very sweet and friendly girls who like curling up with each other.
My last cat would not tolerate having another cat in the house at all and would howl like a banshee if she saw one out of the window.
They are all different.

@BrunoJenkins

Cats are naturally solitary and don't need or want a "companion"

If that's true, why are feral cats almost always found in colonies?

I don't think cats are as solitary as some people like to claim. I don't know anyone who just has one cat - everyone has at least two (many more in most cases) with no issues at all.

My last cat would not tolerate having another cat in the house at all and would howl like a banshee if she saw one out of the window.

My last cat was the same, which really upset the cat from the upstairs flat. He was mates with the cat who lived there before. She threw a hissy fit royale if he tried to come in.

My concern is that the new cat will be bored during the day while I'm out at work (home working not an option thanks to rubbish internet). He will have a catflap to go out and toys, if he wants them. He will be coming from a busy home to a practically silent one.