They're high energy - we're not just talking 1-2 hours a day. They're sled dogs. Most of them need 2+hrs a day.
They need a tonne of mental stimulation - a quick brain game or snuffle mat will not cut it.
If you cannot meet the above, you'll have serious issues with destruction of your house at best...and pretty much every negative behaviour you can imagine, at worse. If you can meet the above...then you need to be prepared for the below.
They're not particularly great with children or other dogs (even when socialised young) so if you have children I would swerve.
They're stubborn as hell. And a rescue? Probably not been trained properly - trying to correct that behaviour will be a bloody nightmare.
And they are big. We're not talking 'Labrador big' where it's got a bit of muscle but an average human can hold it back. We're talking solid muscle. Even though they're a similar size to a Golden, they are way stronger.
They have a tonne of (expensive) health issues - dysplasia, eye issues etc.
They shed loads. And I mean loads. You're looking at daily brushing and hoovering.
They're lovely dogs. But, the only person I do know who has them lives in Northern Ontario and she wouldn't ever have another one - even in the climate she lives in and the life she lives, she still struggles to ensure hers are adequately stimulated and exercised.