1/3 acre for 6-8 geese should be sufficient for just ordinary grazing. However, 3-4 geese can and will control grass growth on a full acre with no problem. So, you may find that you will need to supplement fresh greens for them regularly. I would still make sure that your neighbors are aware of the amount of noise that 6-8 geese can potentially make if for no other reason to just be a good neighbor. Planning on breeding has little to do with it if you have both males and females. They will breed and unless you regularly take their eggs away from them you will have goslings. As cute as they are you may find that your flock grows by leaps and bounds rapidly. Six geese can easily produce a minimum of 6-12 goslings a season and probably more than that. So, your 6 would become 12 and they would become 24 and they would become 48 really fast. As for housing. Remember that these are birds and are flocking animals. They want to be together. You could get six geese and six dog houses (that is houses for dogs not geese) and find that all six of your geese try to sleep together in one house. You and they will be much better off and healthier and safer if they have something that is built for geese and not some other animal.
I am not trying to discourage you but to help you look more realistically at what you are about to undertake. Geese are regal and dynamic birds. They are, in many ways, the emperors of the domestic waterfowl world. They deserve the trappings that implies. I think that last year when you had your first geese I may have suggested that you look carefully at why you want geese. And, I would suggest that you do that again. Be honest with yourself so that the geese you do get will have a happy and healthy life. If your birds are scheduled to be shipped to you in April you still have time to adjust your order to something that may be more realistic for your goals. The birds you do get will be happier and better off if you carefully and honestly evaluate your desires.
I sincerely wish you the best but I also would hate to see you take on more than you may be ready for. Not only for your peace of mind but for the wellbeing of the geese you get.