They're either one-off old apartments (or old large buildings converted, sometimes badly, into apartments) or renovated warehouse spaces. 

Needless to say I did not buy one as our temperature regularly gets down to -20.

I like these amongst ,many other right nowREXR - (Rexford) they are a niche (sub-specialist) in industrial warehouse/distribution/manufacturing in the southern California only urban or Infil area, they are not international like PLD - prologis, their MOAT is that SO-Cal has geographic limitation to new inventory, so they have rent pricing power that industrial in rest of country doesn't, also 26 million people in so-Cal and the 2 busiest Ports in country, their earning/revenue projections next few years are best in class, and they are cheaper on price to book than PLD or others, I own some and will buy a lot more in upcoming Recession, likely in next 6-12 months, when publicly traded equities will likely slide by 20-30% although their assets (physical buildings) are only going up in valueVICI- (casino REIT), used to be part of Cesars palace, then Caesars spun them out in 2018, to do sale leasebacks of their properties to take all that physical capex off the books.

I saw a lot of vacant warehouses / buildings that would be great condo / loft conversions. 

Requirements, 10 x 20 bunker, "solid" door, water and humidity dry, temperature moderate or controlled.   

You may find a lender willing to warehouse the deal but those are very rare.

IG: @MattPriestJr I have properties that I rent by the room in King/Pierce/Snohomish Counties.Many pro tips.For heating, I use Nest Thermostat and "lock" the temperature on 68 degrees. 

The cap rates in those asset classes have already compressed and they are saturated with people looking to deploy active and passive income into.For over 10 years, I have been screaming from the mountain tops to invest in office, retail, industrial, land development, flex, warehouse, mixed use, restaurants and conversions.

Do you know what temperature the tenants have the heat at?

I have one contractor who is working on my Warehouse, I love him.