A one-way agreement builds the buyer
Where a business has a single owner, an individual, usually a key employee, can agree to buy the business, and the buyer typically purchases life insurance on the owner to fund that purchase. The successor does not have to already have capital. The agreement creates the buyer before the buyer can afford to be one.
Source: North American Company for Life and Health Insurance, Business Planning: Buy-Sell Agreement, 1804NM-9