Finding properties for affordable housing / supported housing / elderly

We are fairly new to the affordable housing market and interested in what experiences and models people have used to acquire properties, outside of a straight forward purchase.

There has been a lot of negative press surrounding long term index linked leases in the supported housing market, but I would be interested to understand situations where long term leases have worked for the provision of affordable housing / supported housing/ elderly, are they attractive for organisations who cant access the bond markets, as a way of getting access to the properties they require, and how could the long term leasing model be adapted to reduce risk and satisfy the regulator?