Your free cash flow was $80,000 a year and it's reasonable to expect the loan to be repaid in four years,
4 x $80,000 = $320,000.
If the down payment were $80,000, then no more than $240,000 (or $60,000 per year) would be available to make interest and principal payments on the loan, and to provide the owner with some return on the investment ($320,000 - $80,000 = $240,000. $240,000/4 = $60,000).
If the owner expected a 20 percent return on this $80,000 down payment, that would translate to $16,000 per year, further reducing the amount available to make debt payments to $44,000 ($60,000 - $16,000 = $44,000).
An annual payment of $44,000 could support a four-year loan of approximately $139,474.08 at 10 percent interest, or $145,733.58 at 8 percent interest. Add the loan amounts to the down payment, and you arrive at a total purchase price of $210,685 at 10 percent, or $225,000 at 8 percent. If the lender is willing to finance the deal for a longer term or a lower rate, a higher price would be possible.