@StarFleet Carl
As an example, my personal bank has a limit of $25,000 on a single electronic transfer of funds - buying something with my ATM card, with a maximum per day of $100,000. But I could write a valid check up to the maximum amount in my checking account. Presuming that is acceptable to the seller, that also counts as 'ready money.'
Except, in most cases, the term 'ready money' implies that there's a distinct need for discretion, whether it's purchasing a 'slightly used' product with a questionable origin (i.e. 'It fell off the back of a truck, I swear!') or the stereotypical drug buy, 'handy money' is intricately tied to questionable decisions, even if it's a simple as purchasing the leftover athletic equipment of your friends ex-husband, so she can 'get it out of my house!'
The idea isn't that you can get the money, it's that the money is already in your hand, not giving you sufficient time to question the wisdom of your decision. That's why the term is not used very often, as it has such precise context.