I think you need to think about how much the dog will be alone. I personally think as long as a dog like this has plenty of time every single day, several times a day outside to run around living in an apartment isn’t an issue. I had a lab that rarely went in our small garden. But retrievers are working dogs who need lots of exercise - when younger that’s 2 hours a day to run/play/retrieve to be happy.
Do the parks alllow off lead dogs? A courtyard isn’t going to cut it, not pleasant to toilet on/and a lot of working dogs won’t wee on anything other than grass. So you’d need to be prepared to take the dog to the park at all hours, including last thing at night. Is that safe?
They don’t like being left alone for long periods of time. You can work up to four hour periods but really they aren’t getting the best life if that’s more than a couple of times a week.
They also shed, a lot, goldens also require regular grooming, so that’s at least an hour a week. Or a cost at a groomer. And the bigger the dog the more worming/flea treatment and food costs. not to mention if they need an anaesthetic or any other medication as it’s calculated by weight too.
They are fabulous dogs and great company but you would need to be sure you could meet their exercise and stimulation needs. If you are on holiday/going out after work/going away for the weekend what would you do?
to me it’s less about the size (apart from cost) and more about is the dog’s temperament or breed traits suiting your lifestyle?
And no dog likes being left alone a lot, some - yes even the small ones- will destroy your house and bark if they are unhappy.
the other thing that occurs to me is that you are in your 20s so your life is likely to look very different in 15 years when any dog you get as a pup is likely still with you and elderly. If you had, for example a young family by then that’s a lot of caring responsibilities, not to mention cost, insurance increases with the age of a pet. Particularly ones prone to joint issues like goldens.
I’m not saying don’t get a dog, but you’d have to think through all these things very carefully. It’s a far bigger lifestyle change than most people anticipate. And it’s all on you, since you live on your own. Personally I’d start borrowing a dog to see how one might fit in with your life before you commit.
Our lab which are very similar in breed traits to goldens, died in December at 14 years and I currently look after someone’s 9 year old golden a couple of times a week as we aren’t ready to commit to the time or cost of another dog/jobs in flux and I need to be sure to be fair on any new pet. As a guide to cost, our lab, with no underlying health conditions was costing £40 insurance (this went up as he got older) £40 food. Per month. Joint injections at £130 a pop every 6 weeks as he had arthritis in his shoulder which started when he was 12. Dog walker for social walks with a group twice a week at c84 a month (which was a nice to have, but I felt the group walk gave him a lot of stimulation when he couldn’t fetch as much or run as fast/far) annual vaccinations and working/flea probably £240 per year. Rabies and pet passport ran into £100s as we took him on hols, boarding would have been more. So you could easily spend £5k a year before you look at equipment- leads/beds/toys/grooming kit or additional treats, or training classes etc.
You need to consider all these things as it’s an awful lot about what you can give a dog over their life than what they’ll add to yours.