If you are wearing wool suits in the summer, then there is something wrong with you anyway.
No, I wouldn't live in a walk up, not because of the heat, but because of the inconvenience.
Getting home drunk? 5 flights of stairs, I'd end up on the stairs sleeping
Rushing home to the toilet - Be a pain to attempt to run the 5 floors, maybe thats why people piss on the staircase
Visitors - No one would want to visit!
Shopping - I don't do my weekly shopping like in the UK, so it wouldn't be as bad, but I still don't want to walk 5 floors with anything
Walking in lantau peak in mid-summer heat - that's by crazy people's choice, but also once in a blue moon, not on a daily basis.
You got to remember the main reason you are buying to let; to get a return in investment. If you are narrowing your market, then there is high chances there may be times you won't be able to rent it out, to me that means risk. Is it worth it? Even if you buy it at a good rate?
An old walk-up as an investment or a source or income? No.
If you want to live there, buy it by all means.
Surely it depends on the yield. With a high enough rental yield you're protected from void periods and adequately compensated for risks like the building getting compulsorily purchased by a developer.
I might consider it for 20% rental yield but wouldn't touch it at 5%.
Everything has a price.
There are hassles to walk ups but generally you pay less both as a rental and as a purchase. You will always find tenants, it's just a matter of price and how nice the flat/building/neighborhood is...
The lazy/drunk/old/unfit will obviously be put off but personally, I see this as an opportunity to get a deal. Some of those walk ups are dumps and I wouldn't touch them with a ten foot pole but I've seen some well maintained older buildings with outdoor space that were quite nice.