Where did I claim that it was uncommon?
And as far as I can see the OP didn't state that the landlord was suspicious of him because he paid cash; paying by cheque or transfer would not provide any proof that the tenant has a steady income or sufficient funds either.
Grunt, paying cash is perfectly normal here in Hong Kong. If I had something to hide, I wouldn't sign an agreement in my own name.
The landlord went ahead and signed the lease today. Looks like I have myself a new flat.
Thanks. Now for the inspection, pictures and 'handover ceremony.'