Just had a call where this came up and thought I'd post about it...
'Planning gain' is when you obtain planning permission on a property and it adds value.
Some people buy property, get planning permission and then sell - without developing it.
Less risk, less cost, less time taken.
Planning gain can be a great strategy for people who have the contacts with planning consultants, architects and the time to hold the asset whilst obtaining planning permission.
I have in the past obtained a property 'subject to planning permission being granted'.
Which means you agree to buy the property IF planning permission is granted. Then you purchase it for the agreed price and immediately sell it for a profit.