Does anyone know of a company that operates financial guarantees?

I need a company like this to help me

For example: I deposit money into someone else's betting account and use his account to place bets. The guarantee company guarantees the safety of the funds I deposit into other people’s gambling accounts

Hi, I don't think this is a good idea because you can break casino rules and when it comes down to it, it may not turn out well. 

Additionally, have you ever heard of a proof of the origin of the money ? Such documents are usually asked from players in such situations to make sure that no one else is funding the player's account.

So what you are asking is strictly against casino rules and I don't think there is any profit in it. 

So I warn you to stop making such offers.  

Sure, there are companies that provide financial guarantee services for various purposes, including ensuring the safety of funds in specific accounts. However, it's crucial to ensure legality and ethical considerations when using such services for gambling activities. I'd recommend researching reputable financial guarantee companies or consulting with a financial advisor for guidance tailored to your situation.