The solution is to build social housing, of all types, in sufficient quantities that can be rented by people on low and middle/average income, with rent control. Built to modern standards with energy saving and environmental control baked in.
Funded through institutional investment, it would provide a steady, regular return, which is what they look for. Maintenance can be through non-profit companies which can train and employ plumbers, electricians, decorators etc to maintain the buildings as necessary.
Low rents enable people to save deposits to purchase private housing if they want. Low rents also take the heat out of private rental market, releasing previously let housing back into owner occupier market.
Politicians from all sides should be working together for cross-Party consensus on a long term plan to sort this issue out. Housing should not be politicised.