don't think that's true, i was a renter before 4-5 years ago and every place i moved into required proof of income or guarantor's income. i think it's pretty standard, not a recent thing. i don't understand why there should be legislation to prohibit landlords from requiring it. renters are borrowing. they are borrowing the house they are living in. i don't know why it would give landlords "unfair" bargaining ability either. i put up an ad that says you can rent my place for $1,000/month. you email me and ask if you can rent it. i check your income, credit, and run a background check and if everything is ok then you can rent the place. i'm not going to magically jack up the rent because i think you could afford it.
when i rent out the home i currently live in you're damn straight i will require proof of income, credit report, and a background check. if you don't like it then you don't have to rent from me.