Together, the three properties at 5-9 Melba Street total more than 2500 square metres of land and have the potential for up to 17 dwellings.

The combined corner block is RZ3 zoned, making it suitable for a townhouse development.

Market sources indicate a block of that size and zoning could fetch around $7.5 million.

Local firm DNA Architects has illustrated two possible options for the site, which has a plot ratio that permits 65 per cent of the land to be developed.

One is a complex with 12 townhouses and the other is 17 townhouses with basement parking. Both are concepts only and would be subject to approvals.

Steve Lowe of Agent Team Canberra is marketing the blocks for sale in one line and said it was rare for neighbours to work together like this.

"I sold number nine Melba Street late last year to the current owner and the reason that he bought that is because he was friends with the guy that owned number seven, who was friends with the guy that owned number five," he said.

"Each on their own is not worth as much as the bulk lot.

"So it's definitely a good idea if people can communicate and collaborate."

CoreLogic records show 9 Melba Street, which spans 872 square metres of land, sold in late 2021 for $1,735,000. The property is currently operated as an Airbnb.

The other two properties are currently tenanted. 7 Melba Street last changed hands for $910,000 in 2017, while 5 Melba Street sold in 2006 for $445,000.

Mr Lowe said the sale price of the blocks may depend on how the buyer intends to use the land.

"It all comes down to how people want to split it all up, if they wanted to do four or five duplexes or the 17 units," he said.

"So it's price on application a moment."

While it is rare, instances of neighbours selling together do happen in Canberra from time to time.

In Kaleen, two neighbouring blocks sold last year at 8 and 10 Callabonna Street for a combined total of $2.4 million.

The blocks span 1855 square metres of land and feature RZ2 zoning.

Selling agent Sebastian Gutierrez of Ray White Canberra said sellers who are thinking of teaming up for a sale should consider how development-ready the blocks are.

He said any additional costs associated with developing - such as leveling the land or tree removal - could impact the eventual sale price.

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Already the Downer blocks are piquing the interest of builders of medium to large projects and interstate developers.

"We are reaching out to and have interest from potential buyers in Sydney and Brisbane, who see Canberra as a good investment over the long term," Mr Lowe said.

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