I do have some Guardian homes for my puppies and it has been a pretty good thing...but be certain that you negotiate the contract carefully because you will be bound by it if the breeder insists.
For instance, I had one Guardian (I adore the couple) and after the first litter, they asked if they could have the female spayed as they felt that it was much too hard on them to have her away for that long.
Well, I allowed it because this couple are very special to me, but it was a huge financial hit...it takes 2 years to prepare a dog for breeding and it is expensive to test...and raising another puppy to take its place takes an additional 2 years and testing AND finding another guardian...so many breeders would not have allowed this.
Also, the breeder is the legal owner of the dog and can make decisions that you may not agree with...so be sure that it is all ironed out beforehand. Otherwise, you may find yourself in some serious disagreements and have little, if any, options.
It is not easy because the breeder will want to have marketing pictures, you have to check with the breeder before you get the dog groomed, and you may be required to groom the dog more than you would want to...
If you are very attached to your female dog, you may have to give her to the breeder from breeding to whelp to weaning of pups...this could be 6 months!
Also, there are risks to pregnancies...
Still, it is a good way to get a quality dog, one that has qualities meant for breeding (great temperament, apperance, color) ...but again, some breeders give you the dog for free, others charge you a pet price and pay you for the times that the dog is bred. There are many different ways to do a guardianship.
Most importantly, be sure that you and the breeder can get along! You will have a relationship for, perhaps, 6 years.