Will you help me decide whether to adopt a second dog?

I have a ten-year-old Labrador – Nerina. I would like a second dog, but there are two points which have stopped me until now:

1. I am not entirely sure Nerina would be thrilled with a new puppy. In fact, I’m pretty sure she wouldn’t be. She is good with all dogs, she plays and greets them happily – but she’d gladly exchange most of them for humans or treats. However, the new puppy would have a different set of rules at first. It wouldn’t be allowed on any furniture, for example, so Nerina would have puppy-free zones. I would also take Nerina on walks without the puppy pretty regularly.

2. Then there’s money. I’m still a student, so I don’t make a lot of it. I wouldn’t be able to pay for a 2000$ surgery. I don’t have any rationalizations here, but I do wonder whether I’m being overly cautious. Unless I’m being responsible? I do have the money for dog food – always and high-quality, even. I pay for the vet whenever I need him, and Nerina is on pain meds for a hip issue. The trouble is, I don’t know whether I will have more – or less – money anytime soon. Then again, how sure of that is anyone, ever?

I want another dog – despite the above – partly because I’m scared of Nerina dying, I think. It will be a while, but I would not like the dog-less phase at all. Also – I just…want another dog. I can’t explain why, but I trust all of you have wanted something at least once in your lives, so you probably understand.

Thoughts?