For ease of use, you can't beat the Client Paid Hosting plans. You would create a Stripe account and link it to Panoskin. This will then allow you to send invoices through Panoskin to your clients and remember to send them a reminder of when their next payment is due and also charge them when the time comes.
Additionally, you would also not have to pay for the tour up front to help you manage cash flow. When the customer pays, a portion will come to us for Google API costs, Stripe's fee, our fee and the rest will go directly to your bank account that you setup with Stripe. For a full breakdown you can hover over the "How is this calculated" link in the billing tab of each custom tour under client paid plans.
To bill your client you can create an invoice by clicking on the "Create Invoice" button at the billing tab for each custom tour when client paid plans is selected.