Depending on the situation, the buyer may be subject to FinCen vetting requirements. There are no taxes addressed on the escrow side during a purchase. From what I know, the sale of the property will trigger a possible tax liability with a required withholding of about 18 1/3% of the gross sales price (fed and state taxes). There are still year-end tax filing requirements, too, but I can only speak about the escrow requirements. :)
If you have foreign accounts in excess of $10,000(at anytime during the year) - you may be required to report those accounts via filing the Fincen Form.
To avoid money laundering - you may need to vet the money coming from overseas.
You should talk with a lender and see what funds would qualify to use for the 20% down payment.