How, if you are paying both a mortgage for a part of the property and rent for the rest, could anyone ever get themselves into the position to eventually buy the place outright?

The greater the share a shared owner buys in their home, the less rent they will pay to their housing association. If they staircase to 100% they become an outright owner, and they will no longer need to pay rent. Ultimately the decision is for the shared owner to assess their own financial position in terms of buying more shares. 

Of the 320,000 shared ownership homes that housing associations managed last year, 42% had been fully purchased by their owners. However, this doesn't mean that everyone will be able to do it or will want to. Some homes have restrictions due to being in rural areas or places where the building of new homes is restricted. 

All of the details about the cost of this process is available in the lease. The housing association provides details on the costs and the shared owner’s solicitor can advise on the process. 

The government is currently reviewing the rules around staircasing with the ambition to help people staircase in smaller amounts.