Rav and Rabbi Yochanan hold differing views on the implications of a down payment in a transaction. Must both parties fulfill the entire agreement, risking a curse upon breach, or does the down payment bind them only to the part already transacted? The Gemara suggests that a similar debate arises in a tannaitic discussion regarding loan cancellation during the shmita year, when an object taken as collateral doesn't cover the loan's full value. However, in conclusion, the debate is explained differently - does the collateral act as payment or merely a reminder of the debt? Further questions emerge: Can one party unilaterally dissolve a verbal agreement? Rav and Rabbi Yochanan disagree about whether or not this action constitutes dishonesty. Two difficulties are raised against Rav from tannaitic sources and one against Rabbi Yochanan from a different statement he made. Most, if not all the difficulties are resolved. The Mishna delves into laws of ona'ah, addressing overcharging or underpaying. What percentage triggers ona'ah, and within what timeframe can a buyer claim fraud? Rav and Shmuel offer different opinions on whether this percentage is based on market value only, or also on the item's purchase price. Moreover, what recourse exists for a buyer/seller over/undercharged beyond or below the ona'ah threshold?