If I were to buy (this is just something I am thinking of) postal
stamps from other countries and have a stock of them and charged a
service fee, would anyone be interested in buying them?

It'd have to be worth my while. I'd have an enormous expense up front
on the purchase of the stamps, the overseas phone calls and
tax/shipping etc. (if any are taxable and I know Australia did charge
me before). You'd have to pay all costs and a fee extra...

It's just a thought to help people here who have no ability to order
in bulk or have credit cards etc.

I'd need a roll count (ie how many stamps you'd like to buy, which
countries etc). It may not be worth my while... we'll see.