We have two dogs. One recently rescued and an expensive, health prone breed. Big insurance bill!
We're high earners, but we have to make a lot of financial sacrifices for them. We're very lucky that we have a sitter who will come in and stay with them if we're away and doesn't charge the earth, but quite honestly, if it weren't for her, we'd really struggle, as we go away a lot. Well, we just wouldn't be able to go away actually.
Also, our first ddog had behavioural problems and we forked out quite a lot for a behaviourist in the beginning.
So for us, it's not the cost of food, toys, bed, initial cost of dog, it's all the ongoing, fluctuating payments.
Honestly, if you don't currently have a decent amount of disposable income, I don't think it's the most sensible idea.
That said, the fact you want to rescue is fantastic and if you can make sacrifices, i.e, things you could easily live without, then do it!