It's a viable business model in a lot of markets but those places have very different market conditions compared to NYC.

There are a lot of legitimate reasons that landlords are hesitant to take vouchers (Ex: the system is slow to process the paperwork which means that the unit sits empty for months, additional compliance and inspection requirements which can be difficult and expensive to navigate, fear that the voucher will be withdrawn, etc.).

I see a lot of articles about tenants having trouble using them but nobody ever attempts to explain the reason is primarily due to the inefficiency of the government organizations providing them.