So you mean rent to buy not buy to rent as in the title!!!
Im involved in one now. Private owner and private buyer, not a developer. Buyer interested but was concerned about any noise so asked about a trial rental period.
Owner agreed to a 3 month rental. The price was fixed in the contract at the end of the rental term, the rent does not contribute to the purchase. On the 15th september the buyer either buys or moves out and the property is back on the market.
The owner gets some moent towards his outgoings and the buyer can be satisfied either way.
If you go for a longer term then you can have a clause stating the money paid in rent is deducted from the deposit, but really you can make up any agreement to suit both parties.