Will guppies come out deformed or sickly if they inbreed?

hopefully after we move i will be getting guppies, i was thinking about breeding them. mainly to get me away from the computer because frankly im addicted to it. i want to know if they will be all deformed and sickly if they inbreed or will it not matter, i was thinking about getting 6 males and 6 females, (3 breeding males and 6 breeding females 1:2) i want to have a 2' tank for females and use my 3' for the males util i get my 1 cubed meter* for the actual display of males then the females will mostly go in the 3', and i will use a couple of 1' for breedeng and raising. if they inbreed will the fish be less attractive and healthy or make no difference? and if they're only half brothers/sisters will that make a drastic difference?