Trail running in 中山 with China Construction Bank. Don't know exactly how it works. Seems custodian account being managed by a gov't body and a bank rather than a law firm / real estate agent. Buyer and seller may have to open an account at the same bank which provides such custodian service.
存量房 = 2nd hand flats
中山市住建局积极推进存量房资金监管工作
2021-1-11
https://mp.weixin.qq.com/s/OjF4b_qaRTMKGDDriMn_Lw