hello, (this is related with Solidity) I need to create a smart contract for a real state property (house) sales, between three persons:

1) I am the seller in my country.
2) The buyer is in another country and can not fly yet for a few reasons, but want to buy it.
3)The third person is the cosigner in my country as a guarantee.

I will like to know if there is some one that can help me with this, and how much could be? or any information regarding a platform that can build a smart contract with this characteristics?