G'day. I'm no greenthumb but I have friends who are. They have grown many avocados from seed but none of the trees have fruited yet. Aparently they take many years.

The bloke on the local radio garden show says that if you want avocados to fruit in a couple of years there's only one way. That is to buy a small grafted tree form a local nursery.

We live in the tropics so not sure if it is the same for other climates.