A Sydney convenience store owner set fire to a shop in 2014, killing three people, because he wanted to get out of a five-year lease on his failing business, a court has heard.

Adeel Khan was charged with murdering Chris Noble, as well as Bianka O'Brien and her baby son Jude, who lived in separate units above the Rozelle shop.

Mr Khan had previously pleaded not guilty to the charges.

In the New South Wales Supreme Court, prosecutors said Mr Khan had placed up to 10 plastic containers of fuel around the shop and laid fuel-soaked cloth trailers between them.

It is alleged Khan lit one of those trailers under the back door and the force of the massive explosion, left him trapped beneath a large fridge.

Only his hand was poking out when emergency services arrived.

Prosecutors alleged Khan knew Mr Noble and two other men were living in the unit directly above his shop and there were people living in the unit above the adjoining mobile phone store.

"He was prepared to accept the real risk of people dying as a result of him setting fire to his shop," crown prosecutor Mark Tedeschi QC said.

The court heard Khan realised soon after acquiring the business in December 2013 it was not going to be as profitable as he had hoped.

"It was very quiet and the takings were meagre," Mr Tedeschi said.

It is alleged Khan knew the store had to be destroyed, not just damaged by fire, for him to be cleared of his obligation to pay rent, which he could not afford.

Prosecutors also said Khan planned to draw on a contents insurance policy.

"He decided to set fire to his shop to resolve his financial predicament," Mr Tedeschi said.

The court was told that days before the fire, Khan purchased almost 40 litres of fuel, which he pumped into four separate containers at a petrol station in Croydon Park.

This was captured by CCTV cameras.