Hello @Recertified
Your question is quite generic but I will try to answer it.
While there are solutions which are paid for on a monthly basis, most extensions require one-time payment plus updates if needed.
As an example, here is what we offer our clients:
- 120 days of free support and updates are included with an extension
- 50% off on updates after that period (optional).
I believe that before deciding on your budget, you should make a list of the features you need, then enumerate those which are not included in Magento out-of-the-box and finally list the extensions suitable for you.
You can find our extensions by clicking on the link below.
Hope it helps!