A unit in Riccarton, Christchurch, is vacant after weeks of advertising and a cash offer to potential tenants.

Christchurch landlords are using cash incentives and free rent to lure tenants as intensive housing development contributes to a surplus of rental units.

Deals on offer include a $1000 cash-back offer, rent-free periods and no letting fee.

It is a far cry from the post-quake rental shortage, during which people were found living in garages, cars and crowded rooms.

The city's average weekly rent is now around $380, down from a high of $435 in early 2015, according to government bond figures.

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The $1000 deal, offered for a tenant signing a 15-month lease on a four-bedroom Riccarton unit, has not been taken up and the property remains vacant after weeks of advertising.

"There's such an oversupply and there are so many units now. We just thought we'd try something new," said the property's leasing agent, Lois Paton, of Westside Real Estate.

"But we've had nothing, no-one suitable."

The Brockworth Place unit, described as sunny, in excellent condition, and a short walk to Hagley Park, comes partly furnished for $395 a week.

​Many earthquake rebuilds, especially in the city's inner suburbs, have replaced older homes with row of units and boosted supply.

Consent figures show apartment and other multi-unit developments are being approved at five times the rate of several years ago.

Russell Forward, who has been a landlord for 45 years and owns 30 properties in Christchurch's inner suburbs, said landlords with vacant properties should take the opportunity to upgrade them, or lower the rents.

"Things have certainly slowed. You only have to look at the number advertised, there's just heaps. Rents are back where they were four or five years ago."

"Landlords need to put their hand in their pocket and spend a bit of money. They've got to make their properties more attractive."

Trade Me is listing close to 2000 homes for rent in Christchurch, up from 580 in early 2013 at the peak of the post-earthquake housing shortage. Since then repairs, rebuilds and redevelopments have been steadily shifting the supply and demand balance.

Trade Me said the average asking rent for homes in the city on its site was now $360, down about 3 per cent in a year. The fall in rents has been more marked with townhouses, where asking rents are down 5.3 per cent.

Other rental incentives being offered around the city include one week's free rent and waiving the letting fee, which became inescapable during the housing shortage after the earthquakes.

Homes advertised offering a week's free rent include family homes in the popular northwest suburbs of Burnside, Avonhead and Ilam, a three-storey Port Hills house with "spectacular views", and cheaper homes in inner suburbs for well under $300 a week.

Melissa Benge, director of First Avenue Property, said the increase in supply had given tenants "a lot more choice".

"Landlords are having to realise that there's market forces at play. They have to reduce their expectations," she said.

Tenants Protection Association manager Di Harwood said that while there were more properties available, low-income tenants still struggled.

There was a shortage of cheaper one and two-bedroom rental homes to suit elderly tenants. As well, landlords did not want tenants with issues such as bad credit histories, Harwood said.

"Getting a landlord to give them a chance is difficult."

Median rents in Christchurch

(Source: Quotable Value)

Westmorland/Cashmere/Barrington: $450

Avonhead/Yaldhurst: $442

Fendalton/Strowan/Bryndwr: $440

Marshland/Redwood: $430

Ilam/Westburn: $427

Hillmorton/Hoon Hay: $420

Sawyers Arms/Northcote/Belfast: $420

Styx/Parklands: $410

St Albans North/ Mairehau: $405

Redcliffs/Sumner: $400

Halswell/Wigram: $400

Hornby/Islington/Hei Hei: $400

Burnside/Harewood: $400

St Martins/Beckenham/Huntsbury: $397

Bishopdale/Papanui: $390

Burwood/Dallington/Avondale: $387

Woolston/Opawa: $382

Spreydon/Somerfield: $380

Richmond/Shirley: $380

Merivale/St Albans West: $379

Christchurch Central/Hagley: $377

Sockburn/Upper Riccarton: $375

North Beach/New Brighton/Southshore: $360

Sydenham/Waltham: $360

Riccarton: $360

Aranui/Bromley/Bexley: $351

Richmond/Avonside: $350

Avon Loop/Christchurch East: $350

St Albans East/Edgeware: $350

Linwood/Phillipstown: $302

Addington: $300