Nope. I always did them by calculating from owner statements. Several local Realtors and Appraisers as well as people I know who owned SSUs were nice enough to give me data. But I can say the last one I did - maybe a year ago, the vacancy rate had went from a waiting list in 2006 to 30% plus vacancy and locally several SSU owners were discounting to attract business. Cap Rate was dramatically different from 2 years earlier.
If all else fails you need to try and get the actual rents or vacancy from sales and try GIMs or NIMs...They advertise their rates so you should be able to calcuate the GPI.