Assuming this is for a website, first they would need to provide what kind of content will be displayed.
Does their site sell products like a store front? Will you need prices of services to be listed? Will they be providing stock photos?
How much interaction do they expect from visitors? Will the site need a customer relations function such as bill payments or newsletters? Do they only need a contact us page for call back quotes?
Being home remodeling / renovation do they have a portfolio or pictures of past jobs, customer testimonials, other business credentials such as the Better Business Bureau®.
What types of payments do they accept? Visa, Mastercard, Bitcoin?
Company history / about us, service areas / business locations, office hours, phone numbers.
As you mentioned look at other sites, competitor or otherwise, and see what industry specific content they provide and ask your client to personalize similar information. See if they have a brochure already prepared.
I usually ask my clients if there are any other sites that they would like to emulate (not duplicate). This assists in figuring out what the client likes in existing sites in order to get a basis of what matters most to them.
Ask what makes their company stand out above the crowd, find out what they consider an attribute of their services that others in the trade lack. Better customer service, better quality products, better deals and value, money back guarantee. Try to find information that other sites lack that may be an incentive to pick them instead of the other dozen that do not give free ice-cream with every order.
If you send them a list be sure to bullet point each question that needs answered. This should prevent any being missed and needing reiterated wasting said time.
If you are interested I may suggest you talk with a sales person to see what the customer experience will be like as well as glean some knowledge on how to portray the company.
Other important questions are the terms of your employment. Your expectations regarding compensation and their expectations regarding the final product.
I know that is a general statement but it is important that each party knows what the other is needing. Ideally a lawyer reviewed contract is the way to go but in lieu of that get as many specifications in writing as possible. "Sorry sir but it says here you wanted MapQuest not Google Maps"
I hope this helps you move forward in your quest.