Say I've got 10 commercial buildings wich I let to various companies and I've got those buildings together with an equal partner right?

Now this partner and I want to split the lot up so we decide that one partner will buy the lot.
So that partner will pay half of what is invested BUT also an X-ammount for lost revenue since the other partner will no longer have the rent as income.

What is the formula to base this ammount on?

Can anyone shed some light on this please?