David Alexander said housebuilders should have a quota of low-cost rented accommodation, as well as social housing, in new developments.
Mr Alexander, founder of Edinburgh's biggest letting agency DJ Alexander, said there was a misconception landlords had been driving rents higher, as "in real terms rents are no greater than they were 10 to 15 years ago".
He went on: "What I have sympathy with is people being forced to move every six months, when the landlord decides to take it back, move in himself, or sell it. It would be nice to see more investment in long-term options for people to rent."
Longer-term tenancies, allowed under the law which merely sets six months as a minimum, could change the economics for builders and investors, Mr Alexander said.
He added: "If you are building 100 units, 25% need to be offered to the rental market at affordable rents over a long period of time."
The Scottish Government had taken a bigger interest in the sector, in upholding tenants' rights over deposit protection and not paying up-front fees, Mr Alexander said, and it could now incentivise builders to do more for the rented market.
He also warned landlords against inflating rents, saying: "If they become unaffordable, people fall into arrears and we are going to have a crisis."