Good question. i'll check.
It doesn't matter to PayPal how people pay them. You still get the money to your account.
People can opt to use a credit card, or have it deducted from their checking account. That doesn't matter for your receipt of the money.
Same the other way. As long as you've got a mechanism to put money in your PayPal account (which you have to have to set one up), then there's no problem.
PayPal is just the go-between.