Mohammed Mansha Abbas, Mohammed Zulfqar Abbas, Mohammed Vaqaas Abbas and Imran Shan were jailed for nearly 20 years at Leeds Crown Court on Tuesday.
A fifth man, Nasar Munir, was also convicted for his part in the fraud and will be sentenced at a later date.
The court heard how the fraudsters scammed a number of elderly victims across Yorkshire by cold-calling and acting as tradesmen selling home security and improvements.
In a series of chats on messaging app WhatsApp, the criminals discussed their victims with disdain, identifying their "perfect profile" target as a "single lady 89-years-old" who was "blind", "disabled" or had "Alzheimer's".
The crimes came to light after a series of complaints about the Cleckheaton-based company Bespoke Home Security Ltd, and Bespoke Home Improvements Group Ltd, over the way it was conducting business.
Shan, Munir and Zulfqar Abbas, were each stated as the company's directors, while Mansha Abbas held a controlling interest despite already having been banned from being a company director.
An investigation by Trading Standards and West Yorkshire Police found Munir, of Bradford, had set up a call centre company under the alias Mohammed Nasar called National Survey Line Ltd, which was based in the same building.
Victims of the fraud were initially cold-called by National Security Line, with staff reading off dishonest scripts talking about rising crime rates and so scaring them into thinking they needed to install better security measures.
The five defendants each carried out the role of salesmen who would visit their victims later the same day, if they agreed to a home visit.
But the rogue tradesmen would often stay at the victims' homes for several hours, using high pressure selling tactics coercing them into signing up to contracts for over-priced and unnecessary work.
In several cases, the victims were told they were eligible for a Government grant towards the security work, despite no such grant existing.
The defendants, in some instances, would take the victim to a bank to secure deposits, while victims also had loans taken out in their names without their knowledge - the repayments for which they would not have been able to afford.
A total of 28 victims were identified by the Trading Standards Authority.
In September 2016, warrants were executes at the business premises and home addresses of three of the defendants, namely Zulfqar Abbas, Vaqaas Abbas and Shan.
In March the following year, West Yorkshire Police was alerted to victim in Pontefract complaining that £3,500 had been taken from his account after being visited by men claiming to be from a solar company.
The men had told him he had been due a refund and gave him a chip and pin machine.
The report led to detectives identifying eight further victims across the north who were scammed in the same way, including in Sheffield, Manchester and Blackburn.
Later that same month, police arrested Munir and Mohammed Mansha Abbas.
An iPhone seized from Munir revealed a series of messages mocking the men's victims.
Messages included, "that was a great kidnap", "taking people in your car against there will lol [sic]", "hahahahaha" and "this will never get old lol".
Others discussed their victims, writing, "cancelled 20mins after he left the house", "he said he forced me to do acts I didn’t want to" and "let me guess he’s been abused, another one of your victims Nas lol".
Mansha Abbas, of Leeds Old Road, Heckmondwike, was sentenced to nine years after pleading guilty to three counts of conspiracy to defraud. He was also banned from directing for another ten years.
Zulfqar Abbas and Vaqaas Abbas, both of Greenfields, Heckmondwike, received four and a half years and three years respectively for conspiring to defraud while Shan, of Carr Manor Road, Leeds, also received three years for the same charge.
Munir, of Cottingley Road, will be sentenced on March 17.
A sixth man, Roman Le, was convicted of money laundering for sourcing the card machine used in the fraud, and was given a 12-month sentence suspended for two years and 150 hours of unpaid work.
DC Donna Atkinson, of Wakefield CID, said: "I am pleased with the sentences handed down today in what has been a very complex and lengthy investigation for West Yorkshire Police and Trading Standards.
"These men targeted people who were vulnerable because of their age to defraud them out of thousands of pounds.
"They also targeted people who had been genuine customers in the past and abused their trust to steal huge amounts of money.
"These criminals were very sophisticated and manipulative, making money in any way possible."