Legal Question in Business Law in California

Re: contracts

Probably none. The label attached to a legal document has only slight importance in the interpretation of the document itself. The contents are what really matter.

In the abstract, "Contract to Sell" seems to suggest an instrument whose terms have not yet been carried out, while "Contract of Sale" is grammatically appropriate both before and after the sale described within is carried out. Legally, the terms seem to be interchangeable along with "Sales Contract" "Agreement of Sale" "Purchase Agreement" and many other such formulations.

There could be exceptions that are peculiar to the practices of a particular business or trade.