Is it legal to put requirements on housing?

Yes, they are just using the accepted guideline of rent not exceeding a particular percentage of income. If you are lower income and can’t meet the 3x requirement, you will either need to find a private landlord again or perhaps rent a room in someone’s house. I’ve done that before, and it helped me because I didn’t need to put down a big security deposit or get utilities turned on.

They are concerned you won’t pay your rent if you don’t have enough money coming in. Yes it’s legal because they have to protect themselves. Same as if you buy a house, you won’t qualify for mortgage if you can’t demonstrate that you have enough money because bank would be at a loss if they give mortgage to people with not enough money coming in .

If you have a relative who contributes to your bills, could they co-sign? Typically that’s the way to rent a place above your means.

My last landlord was private. My dad can cosign but it's still not 3x rent. Found apartments that accept 2x rent but the place is infested with mice. I make $2090 SSDI and pay $1250 rent now with no problem (dad gives me $1200). I hate being poor. I was an engineer 25 years ago and bought a house in NM for $63K then relapsed and back on disability.
In the hospital last year a girl gave me a list of shelters. I'd rather die than do that.

I have seen a lot of you tube videos about people staying in motels. You can get a motel for like 50 to 60 per night. ( 1800 per month) You may even be able to get them lower if you tell them you are staying a while.

And, because you don't have to pay utilities... many times your overall payment is lower than it would be if you got an apartment.

And they make you bed for you? There are extended stay hotels with kitchens. I think there is even a chain - staybridge.

Would you qualify for subsidizing housing?

I work in hospitality. You do not want to live in a motel/hotel that is $50-$60 bucks a night. Full of drugs and crime.