Hi,
So, from what I understand, what you want is some kind of reservation system.
The products would have a stock of 1 and if someone rent the product for a period of time, no one can rent the product at the same time, or buy it.
I also suppose that the price of the rent would vary based on the number of days of the rent.
Then, for rents, at the end of the checkout, the payment gateway would charge a certain percentage directly and authorize the rest of the rent amount so that the rest could be captured at the end of the rent (and send an email at the same time).
There is no option / plugin ready-made to do all that with HikaShop.
To do it, it will require:
1. developing a reservation system (with an extra table in the database to store the rent periods of each user) so that in the calendar selector for the start and en dates, the system can restrict the days already rented to others. And blocking the buy when a rent is purchased on a product.
2. devleoping a payment plugin so that it would authorize the full amount at the end of the checkout and capture the deposit. And then capture the rest at the end of the rent period. This means that the payment gateway API need to be able to support authorize only and then multiple captures on an authorization. So the first question will be which payment gateway you want to use to accept payments ? Do they have an API which allows for that ?
To give you a price for that development will be difficult without knowing more about the payment gateway. The reservation system itself would cost around a thousand euros to build if we were to work on that for you. A payment plugin is usually several hundred euros of development costs.