Homeowners and landlords already pay rates- a tax upon housing. Your imaginary rental tax persecutes single home owners only- landlords wouldn't be affected, so there's no impact on slowing the property market to be gained by it and it could be sidestepped by setting up a company, selling your house to it then renting back from the company.
Far simpler to base the rates on the last purchase value of the property- landlords wouldn't want to buy for that much as they couldn't rent out a RV $350k house they bought for $1m and make profit due to the rates. If you then close the tax loopholes for making losses on rental properties, you slow the market. Stop foreign purchases of property, even through intermediaries (only citizens & permanent residents should be able to buy) and you're getting close to making NZ affordable for kiwis. Finally, a national database of ownership- one property registered as your home, all other properties deemed as investments with a capital gains tax applied.
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