When I began my career as a Tiler, about 3 years ago.....the customer was very welcome to purchase the setting materials, grout, caulk, tile, even spacers!
However, over these few years I've learned to sing a different tune....
90% of the time, I specify and provide exactly what is necessary. I'm not always loyal to just one brand of products. I'll use the best for each step of the job. In the states we have Custom Building Products, and projects built with this brand are "Eligible for a Lifetime Warranty"....however, Mapei is the other major brand, and they have a very nice mortar that is "Dust Free" (less dust).....I love the initial grip & consistency.
Fellas, this is a very complex subject, and I often quiz myself on whether I'm losing or winning while supplying everything "turnkey".
The internal vote is in for LOFTHOUSE, "You always win when supplying materials, just make sure the customer does specify grout color/sanded/un-sanded."
This way, you do make a profit from delivery, sales, plus you get to keep most of the left over materials for the next job. I keep a covered box in the van for open bags of powdered materials, and always rotate stock to prevent waste. In my opinion, mixing 5 lbs of one thinset with 50 of another is a-okay. (TileSetter/Pharmacist.....same difference)
Another thing,
If I waited for my customer to come up with anything, I'd be about 2 days behind on everything (typical)
The Suppliers see you at their place of business more often when you are purchasing, it's good marketing....being able to walk into a Hardware/Dealer with your company shirt on, dried mortar on you britches, van in the lot. You'd be surpirsed how much business is generated when you are in the public's eye often.
Keep a tidy appearance on the Van/Truck also, it tells them a bit about your performance in their home.
Sale, Sell, Sail....... Make Money, Feed Your Family,
Randy Lofthouse