First time working with an interior designer

Hello everyone, I was planning to work with an interior designer but they’re not available until next year. I got referred to another designer (who worked with them before) and just received this quote:

$20/sqft for the design and work with the general contractor through the project

And 20% purchasing fee (optional, I can do the purchasing myself, they provide me with a list and quotes) but if I go with it, they share all the trade discounts and organize all deliveries. With this they claim I'll save money as most trade discounts are over 20% plus time and headache.

Does this sound like a good rate for interior designer?