that's actually a dream of mine to buy a warehouse/old urban building and turn it into sick ass place to live. the shittier it is on the outside the better because it's gonna be ballin' on the inside. my gf thinks the idea is crazy but whatever...i call it my "bruce wayne complex"
If you're good at plumbing (including risers), sheetrocking, electrical wiring, flooring, running gas lines etc it's more than doable. I went through a warehouse conversion some years ago in the financial district of NYC.
Depending upon your location, heating can be the biggest issue. Around here, most warehouses have huge gas heaters suspended from the ceiling that can be quite expensive to use in the winter and quite expensive to have removed, not to mention the expense of installing another form of heating. Most warehouses are not very cozy or very well-insulated. Big old drafty windows are another consideration.
I'm in Northern-ish Ontario, so if I were to do this here heating would be a huge problem,
My biggest concerns are finding a good way to:
a) Soundproof huge rooms without spending 50 grand
b) Create enclosed sections for the more "private" rooms
I'm not sure about canadian planning, but you might have to re-register from commercial to residential, It could be a HUGE problem.
I haven't even mentioned it to the GF yet. All I know is I want a place to invite friends over for a drink without having to worry about not having room, and I want a place where I could make a mini music studio without using my entire living space to do it.
Oh, and maybe a giant trampoline + pool.