[Desh] and [my roommate] hereby sell all leaven (defined to also include food containing leaven, possible leaven, and all kind of leaven mixtures, as well as leaven that tends to harden and adhere to inside surfaces of pans, pots, or cooking utensils, or the utensils themselves) in their apartment at [address], Philadelphia, PA, as well as any leaven of which they are unaware (whether in the apartment, or owned by either or both of them in any other location), to [my non-Jewish coworker], for a sum of $5500.00. This transfer of possession of the leaven will go into effect at 7:00 PM Eastern Daylight Time, Friday, April 18, 2008, regardless of whether any money has been paid. [Desh] and [my roommate] relinquish all claim to the leaven at that time.
If the full sum of $5500.00 has not been paid to [Desh] and/or [my roommate] by 9:03 PM Eastern Daylight Time, Sunday, April 27, 2008, then all goods (leaven and money) will revert to their previous owners, and this transaction will be null and void from that time on.
This transaction will be valid upon the signatures of all three parties.
(Note: If you definitively know of some halachic problem with the wording here, please don't tell me until after Passover. I really don't want to know. If you just have questions, though, from any background or angle or perspective, feel free to ask!)