It is normal the builder ask for some money in advance to buy the materials before to do the job.

Yes this is normal in cases where material prices are high. I usually see it as a deposit almost.

Yes, it’s normal. It’s actually the first thing you’re taught in when learning a trade. A lot of people have bought all the materials and done the work with no contract being put in place before the works had been carried out, and the customer has just refused to pay. He’s simply covering his back, I’d rather lose money on the labour than my own money on materials. Check the reviews of the builder first because it also works on the flip side, I’ve heard of customers being ripped off also. Hope this helps.

Yes, in some cases builders ask for money to get the materials before the job starts, but some others prefer buying the materials and doing the job and then including all costs in the invoice.

I personally don't ever take any money up front I use a cash float then replace it when the job is completed and paid for

Yes this is totally normal from some builders. I would of explained to the customer that if we agreed to work together I would need part payment for the materials. I personally never take payments until the job is complete , but I feel you need to be clear with the customer from the start