I’m catching a few at moment , but you do need to be in a world !
I’d say 4-8 mins in …
More usually come but never had an instant second one before this.
A few days ago i got 7 whilst farming. Ok i had two double spawns in there but none the less - Need to activate the XP boosted incentive for that … About 2 weeks ago i got two the same which i thought odd.
As for selling my advice is carry plenty and pick the right one for whatever is in demand (previous high val sales and none on or just one with a stupid price !)
I’m getting between 75-400 bc depending on what it is etc… only usually sell common or u/common. Prices are much higher than in the summer .
I often buy them when I see they are under 15 bc … I will make 50-100 on that … also don’t sell them in bulk imo it’s dumb