They should start to bear in 2-3 years, but won't bear abundantly until 5 years old or so. Not sure what your reasons are to want to grow from seed but it would be faster to take cuttings from friends and root those which is very easy to do or just buy a couple small bushes and take cuttings from them constantly. Even just a couple small bushes could give you many dozens of cuttings per year. The advantage is cuttings will produce plants MUCH faster than from seed. The other advantage is you will know the variety, from seed the bushes will be an unknown type and could be great, fair or poor........