You have an "option to buy" the property (usually todays market value) over a terms e.g: 5 years.
Every month you pay the agreed rental price – which is agreed for a term, eg: 5 years
Pay a simple monthly rental price, for an agreed period of time (the term). eg: 5 years
Within the 5 years (the agreed term) you can purchase the property (when you can qualify for a high street mortgage).
When you qualify for a mortgage - you simply exercise your option to buy the house at the agreed price ( congrats now you own your own home and have secured any equity as well).
If you decide not to buy, simply hand the property back "as is".