Bava Metzi 65: The Appearance of Interest; Delayed Payment

Some major points elucidated in today's daf:

• It is important to avoid the appearance of charging interest
• Mishna: 
• an increase in rent can be imposed to begin at a later date
• the sale of a home cannot be increased over time for that is too close to charging interest
• Tarsha, tacit interest, is when an item is arranged to be sold at a later date/higher price as long as these details are not discussed
• Most rabbis agree that tacit interest is permitted but some forbid it
• Tacit interest is said to benefit the buyer
• Mishna:
• one cannot give a portion of the payment for a field and then claim ownership at a later date when the money is available
• one is permitted to lend money based on the value of another's field and then contract to claim the field in the future if the money has not been repaid
• the rabbis argue about whether or not the seller can benefit from these profits
• benefit derived from the field might be counted as interest

Clearly the rabbis are concerned about both well-meaning people and devious people.  They create halachot that take into account the possible motivations of the buyer/seller while attending to the other halachot related to finance, property, ownership, interest, etc.