The seller must also realize he can not expect to control the company anymore. That is important when negotiating a deal that would include post closing purchase price adjustments. A good agreement provides controls based on some expected level of earnings. Typically, consolidators pay on a multiple of the cash flow, and all sorts of factors, such as debt, go into this. If they see a good strategic position, they may pay a higher multiple.
Corporate culture is another matter.
I've seen this in printing and banking. The cultures have to mesh. Owners who stay on, even at the buyer's request, need to transition to a new role and get comfortable with the fact that they're not running the entire show anymore. Many issues can come to light during this exploratory phase, often involving real estate ownership, leasing of real estate and environmental issues. Receivables must be in order, and consolidators want to see a diversified customer base.