All in all, it is legal to assign real estate contracts. In fact, all contracts are assignable by default unless specifically stated otherwise within the agreement. As with anything having to do with contracts, it is extremely important to read the contract you will be signing with any seller of a property.
The assignor must agree to assign their rights and duties under the contract to the assignee. The assignee must agree to accept, or "assume," those contractual rights and duties. The other party to the initial contract must consent to the transfer of rights and obligations to the assignee.
Under property law, assignment typically arises in landlord-tenant situations. For example, A might be renting from landlord B but wants to another party (C) to take over the property. In this scenario, A might be able to choose between assigning and subleasing the property to C.
The assignor must agree to assign their rights and duties under the contract to the assignee. The assignee must agree to accept, or "assume," those contractual rights and duties. The other party to the initial contract must consent to the transfer of rights and obligations to the assignee.