I made this up this past week to hand out in my hometown. Haven't actually printed any yet so I can't give feedback on it, but I came up with the idea on my own (meaning I made it before I read posts to this effect) and I did so to sort of break the ice (dirt? lol) with homeowners. That way, when I knock on the door, it's not an awkward fumble for the words to ask permission, it's a simple and courteous "Hi there. Did you get my flyer? I was wondering what your answer might be."
Me personally, I took up this hobby to find coins for my collection. I have little intent to sell any coins I find, short of gold coins, and even then only my first so I can upgrade to the Garrett AT Pro. After that I will likely keep all of my coin finds. I'd never dreamed of finding historic relics with my MD, like my axe head or sleigh bell, so it doesn't mean much to me to hand those items over if the owner so desires. If I owned a historic homestead and someone found such a relic, I would want to keep it too - and I'd probably display it prominently. What you could do is offer the homeowner your services to clean and/or preserve the relic so it can be displayed, and your only payment would be the continuing permission to hunt the property.
As for jewelry... idk, that part is up to you. But if you find something that the owner (or owner's ancestors) lost and you return it to them, you have restored something of priceless sentiment to them, and that goes a long way. If it's just random jewelry, who cares about a 50/50 split? When you arrived there, you didn't have anything, now you're 50% richer, right? Common logic tells me that if you inform the landowner up front that your goal is to find something for your collection, they will probably let you have whatever you find.
I gave my 2c earlier. This was my quarter