I did one 12 months ago for ex large format, tile on tile if I remember rightly, for two of them.
Thin tile so only 4 courses high and two wide, prime and grip and tiled.
The third however was a little different.
Whilst Jerry is correct in saying they may expect ridiculous things to be done, that’s where it gets sticky.
Personally I will always refuse if I feel it’s unsafe and in danger of hurting someone.
Some shop owners actually think the same, but then I suppose it will depend on the type of shop, this one was a very expensive bathroom store and thankfully cared.
It was to be tile on tile on an upper level also, when I looked at it, I didn’t like what I saw or heard when I tapped the existing tiles, that working hollow sound.
So I asked if I could remove them and start fresh. They were on to a board that resembled the back of hardboard, that slightly rough feeling board that they make commercial temporary partition walls from sometimes, and it was painted.
So I asked owner for a pair of extra hands to steady the upper courses while I remove bottom two.
Reason I started where I did was because I saw one of the corner pieces hanging off and my fear was it would start a chain reaction if it got dislodged while removing the rest.
Oh my word was I glad I did, and fortunately the shop owner was stood behind watching, keeping well back may I say.
As I put my gauger behind the loose tile and slightly moved it, two rows of 14mm 80 x 40’s came crashing down instantly.
Luckily I have lightening reactions, comes from catching tiles before they hit a shower tray or bath I believe.
I managed to jump clear, my temporary helper was well over 6’ and able to still lean over and prevent the top 2-3 courses from going too!
Shop owner was horrified at what he saw and of the thought of what might have been.
So thats what you can be up against, ultimately the choice will be up to you to either comply with requests, or walk away.
I know what I would do in future, for sure.
Oh and the guys who’d did the display previous, were proper tilers apparently!