Hamilton's rental supply is concentrated in the old city, with most of that supply located below the escarpment between the 403 and the RHVP. Rental rates in some of those those communities are basically the inverse of the city as a whole, with something like 2/3 of residents of Wards 2 & 3 renting and 1/3 owning, while Hamilton's city-wide rates are basically 2/3 own, 1/3 rent. Add to this the historic devaluation of real estate in those same areas, mixed in with precarity/poverty rates and you have a problematic set-up for a runaway housing market and the explosion of investment properties.
For decades, banks and buyers had a jaundiced view of these areas, but now the market dynamic scans as Canada's last can't-miss-get-rich-quick scenario. This seller's market has impacted historic rental stock as large houses in neighbourhoods like Stinson that might have been subdivided into rental units have seen owners sell, while many mid-rise and high-rise rental buildings have been converted to condos, taking them out of the galaxy, or flipped to REITs who look at an apartment as a financial instrument.
Wards 2&3
2001: 79,335 population in 38,800 dwellings
2016: 74,890 population in 41,070 dwellings
Supply is relative.