Wealth is not income.

You can be wealthy and still have poor cashflow, especially as a leveraged property owner

Wealth is easily converted to income. People can sell their properties and move to cheaper ones. If we’re gonna run our entire society on the whims of retirees who are taking up houses big enough to raise families, while also preventing all new construction, while also opposing paying their taxes, while also opposing moving to smaller houses, we are just fucked.

For multi-unit housing a cash-poor leveraged property owner sounds like a likely slumlord, so I'd be happy to discourage that situation. More, less-leveraged, property owners instead sounds good.

For owner-occupied, it sounds like someone who made a risky financial decision because of perverse incentives. Which also seems good to revisit.

Also in these cases cash-poor is not low-income. It's likely to be high-income+high-obligations the way you describe it. Hard to get all that leverage otherwise.

It's not just slumlords though.

Rental yields are so low in the UK compared to the cost of finance, tax and maintenance that being a landlord has become completely unprofitable, which means the rental sector is falling apart.

Pretty much no landlords in the south east of England are cashflow positive on a monthly basis, and if they are they are yielding less than government bonds