Need help figuring out a word for a certain situation

Solution 1:

The closest I can think of is escrow. It refers to giving money to a trusted third party, who holds it (in escrow) until goods or services are delivered. I have never heard it applied to holding goods as well, but see no reason why it shouldn’t be.

Solution 2:

I think the word you are looking for is "broker."

Wikipedia: A broker is an individual or party (brokerage firm) that arranges transactions between a buyer and a seller for a commission when the deal is executed.

It can be both a noun and a verb.

Broker - noun - a person who buys and sells goods or assets for others.

verb - arrange or negotiate (a settlement, deal, or plan)

Solution 3:

A newer variant could be "middleman". It is used in many virtual trades where A wants to pay in real money for B's virtual item (game / game time / cosmetic items, whatever) but of course no one wants to send their items first, then they ask a reputable middleman to hold both items and then trade with both of them.