Start the source-of-funds work now and file the petition only when the capital has actually been invested or is actively in the process of being invested. The estate documents and the decedent's history take longest to gather; the transfers themselves are quick once the money is in hand.
Gather the history while the money is still arriving
An EB-5 petition must be filed with the investment made or actively in process, so the wire to the regional center's escrow or the enterprise is the last step before filing, not the first. Everything that explains the money can and should be assembled before that. The estate's documents and the decedent's tax and asset history may take time to collect, especially when records have been archived, and translations add time.
The house sale produces its own documents on closing and the purchase history can be pulled from the land registry beforehand. Sequence the work so that on the day the inheritance distribution and the sale proceeds have both arrived, the file already contains the source narrative, the supporting exhibits and the translations, leaving only the consolidation, the currency conversion and the wire to document. Then file.
If a child is approaching 21, an earlier filing with a partially funded investment that is actively in process may be justified, but that decision should be made deliberately with the regional center's documentation, not by accident of timing.