Attribute applied to cart, not product?

This might sound strange, and I have searched vigorously for this..

...but I need to know if anyone has any thoughts on applying an attribute to an entire shopping cart.

For example, we are creating a cart for a furniture rental store. The customer needs to be able to select furniture and add it to the cart, and the price will be the price/month. However, they then need to be able to select a TERM for the rental, that would apply to all items in the cart. The price would then be multiplied by the length of the term in months to create a total.

I know that we could do this per item, and have a drop down box with the term length, but the term length really needs to be global for the entire order. Otherwise, someone is bound to select different terms for different items, and if they decide to change the term, they would have to edit each individual item- which would be a pain and a deterrent to sales.

I am pretty sure there is no existing mod for this, but would it be insane to even attempt such a thing? Would it be more trouble than it is worth?

We are trying to decide whether to modify Zen or start from scratch. I am leaning towards modifying Zen, because it is SO feature rich- starting from scratch we could create the customer minimums with no frills, and it would certainly cost more, too. But if it will end up taking forever and not be very feasible to modify Zen in this way, we may have no choice.

Thank you in advance!

ETA:
We have a significant amount of experience with osCommerce, though it has been a while. But we are new to ZenCart. From what I can tell so far, they seem to be pretty much the same as far as getting dirty in the code.

This would appear to be a nodule creation seperate from attributes...

You might look at the layaway module for some direction as I see this as a "Payment Module" with options

Thank you, Kobra, for that tip. I am checking out the Installment Plan mod since that seems to be the updated Layaway Module. Hopefully with some tinkering we can get that to work. I have read many of your posts on the forum, and you often prove wonderfully helpful. ;)

Any other suggestions are still welcome. :)

Welcome to the Zen Cart Crowd

Anyone have any further suggestions for this? I would really like to be able to add an attribute to the shopping cart rather than individual items. The feature that the thread-starter wants is exactly what I need...

Adding something to the payment screen would work okay, but being able to add an attribute to the shopping cart (which is then saved for the order) would be perfect. Is there any way to do this without getting down and dirty with the MySQL tables and PHP code?

"Is there any way to do this without getting down and dirty with the MySQL tables and PHP code?"

Absolutely not. This will require expert custom coding.

Okay, well good to know. Time to delve into the code.

Thanks for the info.

I have been hoping for something like this since I first startedusing Zencart. I have 4550 products from which a customer can choose and the attribute choice will be the same for every order. It is really annoying to have to choose for each item. I would be willing to share the development cost with others needing this. I will also check out the possibility of hacking the payment module.