As someone who has fostered close to 200 golden retrievers since 1994, my answer is “Maybe”.
This photo is of Holly, the second golden I ever had. She was the sweetest girl. I remember the next door neighbor girl came over every day after school to play Barbie with her.
We had fostered a few pups for short periods back in the early days of our rescue involvement, and then we fostered Nana Darling. Nana was a big, bossy girl raised in a household of men. When she wanted something, she took it.
She lived with us for six months as it was a challenge to find the right home for her. One day after she had lived with us for several weeks she tried to take a frisbee Holly was holding – again.
We tried to keep an eye on Nana and had plenty of toys for both girls, but she pushed Holly a bit too far this time and Holly bit her.
Nana dropped the frisbee and ran to us for comfort.
Holly learned how to handle Nana as Nana never took a toy from her again.
Unfortunately, that lesson stayed with her with any dog who even playfully tried to take a toy from her.
In addition to learning some negative behaviors, your resident dog can get some contagious illnesses. If you have a puppy, avoid fostering at least until your puppy has had all of their vaccinations. My pups have contracted kennel cough and whip worms from foster pups. I know someone whose resident pup got ringworms (a fungus, not worms) from their foster dog.
I think the biggest mistake foster families make is not taking a break of at least a month after your foster dog is adopted.
Also fostering more than one dog at a time can overwhelm your resident dog/s.
It’s also a good idea to foster dogs who are about the same age and activity level as your resident dog. While a senior golden MAY like to have a youngster around, it’s more likely they would prefer to just have a pal to lay on the porch with.
Foster families are often hesitant to admit a foster dog isn’t fitting in as they don’t want to be a failure. Often the rescue organization has no one else to take the dog. (They can always pay to board until a better foster family is found.) It’s best for your family and the rescue if you have any doubts after a week or so to be looking for a new placement.
Your first responsibility is to your resident dog. Dog lovers have big hearts. It’s ok to put your pup and family first. If you have positive experiences you are more likely to become a long term foster family.