In a non-cuddling context I recently encountered a nice idea for overcoming the deposit problem. (Professionals needing them, clients reluctant to pay them.) A professional in a field with a similar business model requires an online gift card purchase from her favourite bakery/coffee shop. (It was Gail's, which is an overpriced and therefore rapidly growing chain in London and southeast England.)
Various amounts were available and thus the requirement could be varied depending on the value of the booking, but the smallest one was only £5 i.e. one coffee and change. I was not a prospective client - the discovery was an internet drive-by - so I don't know the details, but it's obviously a promising system.
History teaches us, from many examples, that it is not the size but the principle of the depost that is more important.