MONTREAL -- A day after a major announcement on affordable housing, a second such announcement came on Wednesday: Quebec and federal government are joining forces to put $100 million into low-rent housing in Montreal.

Tuesday's announcement was about the construction of 1,500 new units, but this pot of funding will be used to renovate over 500 existing units.

They're operated by Montreal's public housing agency, which has long been the subject of complaints about run-down, uninhabitable housing.

One young mother spoke to CTV Montreal last summer about losing her furniture and ending up homeless for a time after needing to move out of city-run housing with her two daughters because of bedbugs and plumbing leaks.

The 517 units to be renovated are a small fraction of the 34,000 total units rented by Montreal's housing agency. But they are the most in need of repairs, city officials say.

Some are boarded up because they've fallen into such serious disrepair. Montreal Mayor Valerie Plante said Wednesday that 100 social housing units in the city are currently unoccupied because their condition is too poor.

That can't continue in a city with such a low vacancy rate and other aspects of a housing crisis, she said. The city needed to find quick fixes to get them back into use as fast as possible.

The renovations will last three years.

The need is much greater, even within that one specific area, housing advocates say. A federation of Quebec tenants who live in affordable housing estimates that Montreal needs $400 million a year for five years to fix a total of 10,000 housing units in bad shape.

It says even the city has estimated it needs $792 million to fix them all. The city admits that fixing 500 units is far short of its own goals at the moment, but that they'll celebrate the funding that they do manage to get.

Plante said that Montreal has 25,000 families now on a waiting list for a social housing unit.

Housing is nearly guaranteed to be a major election issue this fall, and it's something that Mayor Plante's Projet Montreal party has staked some of its reputation on -- with fairly good results so far.

The party promised 12,000 new low-cost and social housing units, and as of late March it was just shy of reaching 80 per cent of that goal by the end of Plante's first term.

-With files from CTV's Max Harrold