SunPower (SPWR) and SolarCity (SCTY.DL) have been on fire in 2013 and one of the big drivers is the solar leasing market. Both companies will generate revenue for 20 years or more from each lease signed, which should add big value for shareholders. But what are the most important qualities in a leasing company? Fool.com contributor Travis Hoium relays the takeaways from talks he had with two industry executives to discuss what will drive the future of this growing market.