One of the businesses with no limitations of installed capacity and extremely high ROE is High end broking. ( Any underlying asset, not necessarily financial assets only ). The typical size of the transaction in the high end broking is at least 25/50 crores and that is just for the starters.
The core competency has to be the right background, right network, right presentation skills and the ability to slug it out on a long term basis with single minded devotion. Like investing, here also , you do not have to have a deal every day/week/month and even one deal a year could be highly rewarding.
Of course, this is not every one's cup of tea.