Avacado growers

[duajones]

I know it is technically a fruit but thought I might get more hits here. My neighbor Frank has two avacado plants that he started from storebought fruit saved seed around 10 yrs ago. One is probably 10 fit tall or better and the other is a scrawny 3-4 ft. He told me about it 3 yrs ago when I asked what it was and also said that it had never bear any fruit. Couple days ago he told me that he had a couple of fruit on it and couldnt believe it was fruiting after 10 years. My question is why? Also wanted to mention that the reason he noticed the fruit is because he noticed a small marble sized fruit under the plant and looked up to find a few more on the plant. Next question is if it dropped a fruit or two, does that mean it will drop more? He also mentioned that he hasnt done much in the way of fertilizing the past few years because he figured he wasnt going to get any fruit from the plant. The area is well watered because he has other plants along side it. Should he fertilize with anything now? If so, what and how much? And what should his fertilizing plan be from here on out since it is bearing fruit now.
Thanks to any that reply as I always appreciate the great info I get here at TV. Any info will be gladly passed onto my fine neighbor

Duane