No, i don't want to ask how to make money. I know how to. I need another thing. All vendors have limited money. They run out of money to spend and i run out of people to sell goods at. This is really heartbreaking, as some of them, especially innkeepers, buy certain goods at very high a price.

1) Does money replenish on a vendor's pool, like the items they are selling?
2) If all vendors in the same area run out of spending gold, am i screwed for good?
3) Actually, is there a storage chest like the one in 2, or the innkeeper service in 1?

I'm not sure how long it takes to fast travel from one area to another, but early on I fast traveled back and forth between vendors in White Orchard and Velen at one point, and their money kept replenishing.

Have you been to Novigrad? There are several of each type of vendor there, and the innkeepers have 2k-3k instead of a few hundred coins.