We really lucked out buying our house earlier this year. The couple had Solar City put a 7.1 kilo watt system on two years ago and pre-paid the 20 year lease. Warrant and contract transferred to us as part of buying the house and we have to send no money to Solar City, our last electric bill was just under $8.
Talking to Solar City on the phone and email prior to buying the house, I found them very easy to deal with.