Asklemmy

Well, the obvious and practical answer is a giant block of some kind of precious metal. Whichever one has enough value per unit of weight that it's essentially an insane amount of wealth that can fit in a fairly small space. That way, you can have a big brick of whatever it is in your closet, chip off bits and sell them off after a little work shaping them. Gold is the obvious pick, but maybe platinum would be easier to work with in terms of turning into a sellable form.

It partially bypasses the whole thing where you have to figure out how to nicer launder big amounts at once, or worry about flooding a market. You just causing use it to supplement whatever income you have, and have that safety net as needed.

However! This ain't a practical situation.

Let's get a little more interesting. Ignore any of the the tricks to try and get infinite uses, that's no fun.

I think the most fun thing would be a personal flight device that never needs fuel, and protects you from the effects of the flight. Magic carpet, jetpack, not really too hung up on the exact form as long as it's usable without drawbacks. Like, if it's a flying carpet, it needs something so bugs and weather aren't messing up the flight. If it's a flying car, it would need to be essentially radar proof unless it came with freedom to go anywhere, and could still avoid other flying things

I think what I would want the most is something that can heal though. Just fix any disease, any injury, like that. Not necessarily aging, I don't want to live forever. I just want to be healthy while I live.

If the object could also extend the life of animals, that would be perfect. To be healthy again, and never lose another companion? That's worth selling your soul for.