That's a personal decision that you will have to make.
When I ask to hunt a private yard, I tell the owner up-front that this is my hobby and that any jewelry or
significant relics I find that are related to the history of the property will be given to them IF they wish.
I also ask that I be allowed to keep any coins, tokens, and/or interesting buttons.
When I finish hunting, I make it a practice to show my finds to the home owner (they ARE curious) and more often than not,
they tell me I can keep everything I've found. On one occasion (two weeks ago), I found a 14K gold ring and after showing
it to the owner, he said I could keep it. When I told him it was worth around $140 in melt value, he said "why don't you
sell it and then we'll split the money". A couple of days later when I handed him his cash, he thanked me and said "you're
an all-right guy". To me, this comment alone was worth more than the gold ring. As I was leaving, he said he would ask a few
of his friends if I can hunt their property.
Also, when asking permission, be sure to leave your name and phone number with the owner, they may say no
when you first ask but might change their minds after talking with other family members. They may be just
as curious as you are as to what lies inches below the ground.
Good luck!