One-time Service + Subscription Service (Mandatory)

I'm starting a web design agency and this is how I want to setup my order/checkout flow:

Client orders for a web design (one-time pymt)
My services requires monthly hosting (most basic and mandatory, Tier 1 package) & other services for higher Tiers (subscription).
Web design is useless without hosting.
The hosting is mandatory. How to add that in one checkout flow when they order the web design service.

Scenario 2:
I have a voice AI that I want to offer.
Client ordered for my services...
My services have different package tiers for voice services...
I have to ask for a set up fee (one-time)
Then I need to charge for monthly services (subscription)
How do I go about it in just one checkout flow. It would look more premium and more organized.