Give the poor money, they can rent what is out there. Most of the problem is then solved.
You are assuming there is something "out there" that is affordable.
I have to laugh at people who complain that they're paying 1/3 of their monthly income on rent/mortgage. About 75% of my monthly income goes to rent and utilities. And that's with my negotiating with the leasing agent and telecom. You know what I had to do to knock $50 off the monthly rent when I moved into the place I'm in now?
I don't have a stove. The manager kept extolling the virtues of the new appliances in this suite when I had to move from my old one (plumbing issues in the kitchen, no insulation that meant freezing for two winters, and the final straw was a flood from the upstairs neighbors). He told me the new appliances meant the rent would go up $50. He also insisted that they were going to remove the carpeting and put in tile, and new blinds and remove the ceiling fan.
I told him that I could do without the stove but would keep the fridge (essential, off course, and I do my cooking with a microwave). I insisted on keeping the ceiling fan, and a damn good thing, too. It made all the difference in whether or not I could sleep during the heat dome we had in the summer of 2021. He kept bleating about "aesthetics" but I told him that for me it was a matter of survival. We're not allowed to have air conditioners here. I insisted on keeping the old blinds because they're more adjustable than the new ones. He kept yapping about "the next tenant." I don't give a crap about "the next tenant." If they keep me happy, they won't need to worry about "the next tenant".
He kept protesting about the stove, saying that I HAVE to have one, in case "head office" does an inspection. They would be Very Upset to discover I don't have one. I told them that I would tell them the exact reasons why I don't have one: I couldn't afford the extra $50/month for the "new appliances". By letting them take that stove away (thus providing me with a few more square feet of storage in the kitchen), keeping the old blinds, keeping carpet in 3 of the rooms (the noise level in carpetless suites in this building is atrocious), and keeping the ceiling fan, they didn't jack up the rent. And the funny thing about the stove is that a couple of weeks after they took the stove out of here, another tenant complained that her stove wasn't working. Good thing they had a spare to give her - the one I gave up.
Or at least until last fall. They gave a small incentive, and due to some new policy with the parking space I don't use but they want me to let other tenants use (I told them that since I don't have a car and no longer share the space with another tenant, if they want to use it for someone else they should give me the equivalent off my rent that would normally be charged for an extra parking space), they increased the incentive by that much. So instead of the rent going up by $100, it went up by $50. That had to be made up from somewhere, and the only flexible part of the budget was food and transportation.
Build the apartments above the retail and office space.
Where do you imagine all this "retail and office space" is going to come from, in areas where the living units would be needed, at an affordable price? For example, most of the stores in the downtown in my city are empty. At least a third of the stores in the local mall are empty. We have a premier who would rather pick fights with Justin Trudeau and shut down renewable energy jobs for ideological reasons than do anything practical to help the non-wealthy here.
Calgary is trying something with living space in office buildings. Since so many are empty now and the homeless situation is dire, they're converting some office buildings to apartments. Of course I rather doubt it's the homeless who will get to live there. And in any case, prospective tenants have pointed out that even if people move into those places, what are they actually going to
do there, outside of working hours?
As for my own situation, apartments that are accessible for mobility-disabled people don't grow on trees. I looked around last year for somewhere cheaper, and found something that would have been $200/month less than what I'm paying now. The problem is that there's no elevator in the building. I can't do stairs anymore. It's a shame, since that place was downtown, within walking distance of some of the places I go, and most importantly it was within walking distance of a grocery store. That's something I don't currently have. But no elevator means it might as well be on the Moon.