if you already have a non-subscription (full license) version of Octane, then you would only be charged $10 per month to access the OctaneRender Cloud (ORC) service. This access renews every month, so that's $10/per month. And if you choose to end the subscription you must just cancel it via your online user account. When you cancel, the ORC service will still be active up until the date of expiry, but it will not renew and that means you will no longer be charged for the next month.
Please note you will also need to purchase render credits to be able to render on the cloud. The render credits will not expire and will stay in your account whether your ORC subscription is active or expired.
The amount of render credits you can purchase per month is limited to $50. You would have to contact our support channel if the initial limit is not enough.
You can upload scenes from your home or office computer to the cloud for as long as the Octane account associated to those computers have the ORC subscription.
To match your version of Octane, you can choose a version in ORC (Advaned Option) while you are setting up a render job. The latest (as of today 30 April 2018) version supported on ORC is v3.08RC3
I hope this helps.
i72630QM @ 2.00GHz | 6GB RAM | 2GB GeForce GT 540M | Win7 64bit