After their own source documentation is assembled and after Canadian tax advice on the sale, and in a single traceable transfer rather than several informal ones. Moving money before the paperwork exists makes the trail harder to reconstruct.
Document first, transfer once
Hypothetical example: a Hampton investor's parents begin sending money in instalments as their farm sale closes, using two accounts and a cheque to a family member who forwards it. Every one of those hops has to be explained later, and some of the records will be difficult to obtain a year on.
The steadier approach is to assemble the sale and tax documentation first, sign the gift instrument, take Canadian tax advice on the disposal and the transfer, and then move the money in one documented transfer from a named donor account to the investor's account, and onward to the enterprise. Build the timeline backwards from the filing, allowing months rather than weeks for source-of-funds preparation, and remember the two-year conditional period extends the plan well past the first approval.