I think the person above answered it weird, basically I've been using PayPal linked with my bank account and debit card:
If you have no PayPal balance and your backup source is your PayPal account it takes around I would say 2-3 business days for it to show on your online statement (if you do online banking) but the funds are sent immediately to the person they are sent for.
I do believe for a debit card it's quicker (maybe) I don't use it as my backup source but I've used my debit card for a purchase online recently and it was pretty much immediately it went on my statement (possibly because I didn't use PayPal as a middleman).
That's my basic experience so far with PayPal and buying, I think the person above you is saying that if you were to transfer funds from your bank account to PayPal it would take a few days, which in that case it would.