The houses, which have a total land area of 1972 square metres with wide frontages to Harbour Street and Market Street, are on the market for the first time as a combined property package.

They are owned by one family, who have held them for a long time.

MMJ residential sales director Daniel Hastings said the properties situated at 17, 19 and 21 Harbour Street were in an "outstanding lifestyle location" opposite Market Square park and within 200 metres of the city's beaches and WIN Entertainment Centre.

"We've called it the best development site in Wollongong and there wouldn't be many better opportunities than this for the forseeable future, or even the longer term, to secure a position so close to the water and the CBD," he said.

Mr Hastings, who is selling the properties with co-agent MMJ director commercial sales Tim Jones, said the location of the properties and the land size made the sale a rare opportunity for potential buyers.

"To have it owned by the one family and be able to present the sale in the one line together is very unique," he said.

The properties, zoned general residential, comprise the following areas: lot one is 727.2 square metres, lot two is 626 square metres and lot three is 626 square metres.

The total Harbour Street frontage is 48.36 metres and the Market Street frontage is 41.15 metres.

The houses have had residential and medical-type uses including a doctor's surgery.

The property package will go to auction on Wednesday, September 23, at 6pm at the Wollongong Golf Club.

Mr Hastings said there was no price guide due to the unique nature of the sale.

"It's one of those situations in which we don't have anything to compare this with, certainly in recent history," he said.

"We would find it very hard to predict and it will just come down to who is there on auction night and what they are prepared to pay," he said.

"There will be some potential buyers who will place really high value on this from the point of view that it's one of the last opportunities in that area."