The Prime Minister and Home Secretary are expected to outline immigration reforms at a Cabinet meeting on Friday.
As the legislation stands, skilled migrants from outside the EU must have a job offer with a minimum salary of £30,000.
It is understood that this threshold will be lowered to £25,600.
Workers from EU countries will be subject to the same rules once the transition period for leaving the bloc ends on December 31.
Workers earning less might still be able to get a visa to work in the UK if they work in a sector with a skills shortage.
Speaking good English or having a strong educational background could also count towards getting a visa.
Last month, a union warned that putting up barriers to hiring staff from overseas in an overhaul of the immigration system would cause "huge difficulties" in social care.
Unison assistant general secretary Christina McAnea said the UK's immigration system has "got to work for social care" but the latest recommendations would not "allow a single care worker to come to the UK".
Her comments came after the Migration Advisory Committee, which advises the Government, warned the proposals were "not perfect" and there were "unavoidable, difficult trade-offs", adding: "The largest impacts will be in low-wage sectors and the Government needs to be clear about its plans for lower-skilled work migration."
Ms McAnea said: "The sector is already in crisis. Placing barriers to recruitment from overseas would cause it huge difficulties.
"Nor would the Government's idea of a one-year visa be any better. By the time care staff have arrived and settled into their jobs, it'd be time for them to leave.
"All their experience and training would be lost, and migrant workers would face uncertainty and instability.
"The elderly and vulnerable people they support would also be left anxious and have their care disrupted."
Mr Johnson promised during the election campaign to introduce a points immigration scheme, based on Australia's, for when the EU freedom of movement rules end.
Under those rules, workers from the European Union and European Economic Area countries can come to the UK to live or work without a visa.