@Julie974 You don't. Guest payments are controlled by Airbnb, not the host. And they don't pay a "deposit". They can sometimes opt to pay half up front, half about a week or so before check-in.
You shouldn't be trying to accommmodate guests' financial woes. They either have enough $ to book a place or they don't. Not your friends or relatives, they are strangers, not your problem.
@Julie974 When guests ask things like this, just tell them that hosts have no control over the payments, that Airbnb handles all that according to their policies. Most guests don't even realize that hosts don't get paid until after the guest checks in- they think you have their $ as soon as their card is debited.