bitcoin escrow exchanger system

hi i need a developer that can build a system like below. its a simple escrow exchanger system for cryptocurrency. where there is a buyer, a seller and us as admin. our clients will be the buyer and the seller. the process is similiar like freelancer.com. where freelancer.com is the middle man to hold the fund between the client and the developer. but for this project the services is to buy and sell cryptocurrency like bitcoin and etc. buyer can buy cryptocurrency offerred by seller and pays to the seller with their fiat money or any other payment set by the seller. seller also can post anything they want to sell and also set the type of payment they want to received. for this system, as long as the buyer can discuss with the seller ( chat system). and the buyer can open a request to the public ( like me open a new project in freelancer and the developer can see the projects) and the seller can also list their service and price. the buyer can search for the criteria of what they want. like estimation buy price, cheapest price. just simple system but can deliver the purpose for buyer and seller if you can do this project please bid. my budjet is not high so please dont bid if your budjet is high.