Because they want step-by-step guidance and support, and design help, and long-term support, not just a few questions answered.
This is a job. The kind of work that IT consultants get paid for. A fair rate would be US$100/hr, minimum, for an independent contractor.



Whatever you do, and whoever you end up working with, document document document. Take.notes.
And I mean on paper, in a notebook, something that can’t crash or get accidentally deleted and doesn’t require electricity to operate.
You’re doing this for yourself, not for a boss, which means you can take the time to keep track of the details. This will be especially important for ongoing maintenance.
Write down a list of things you imagine having on your network, then classify them as essential vs. desired (needs and wants), then prioritize them.
As you buy hardware, write down the name, model and serial number and the price (so that you can list it on your renter’s/homeowner’s insurance). As you set up the devices, also add the MAC and assigned IP address(es) to each device description, and also list the specific services that are running on that device. If you buy something new that comes with a support contract, write down the information for that.
Draw a network diagram (it doesn’t have to be complicated or super professional, but visualizing the layout and connections between things is very helpful)
When you set up a service, write down what it’s for and what clients will have access to it. Write down the reference(s) you used. And then write down the login details. I don’t care what advice you’ve heard about writing down passwords, just do it in the notebook so that you can get back into the services you’ve set up. Six months from now when you need to log in to that background service to update the software you will have forgotten the password. If a person you don’t trust has physical access to your home network notebook, you have a much more serious problem than worrying about your router password.