This question is a little unclear. First of all, if you want to buy a house overseas, the first step is to convert RMB into foreign currency. In other words, buying a house abroad must convert RMB into US dollars.
As for the conversion of US dollars into RMB, this should be the operation of selling houses. After disposing of overseas assets, you can choose to remit foreign exchange into domestic bank accounts, but there is a restriction that you can only exchange 50,000 US dollars per year, and other amounts cannot be exchanged at the same time in the same year. This is the so-called capital control.
There are other channels to convert large amounts of foreign currency into RMB, that is, to convert them into Hong Kong dollars first and then into RMB, which requires a bank card of ICBC Asia.