It has gotten cheaper and quality is much better now in lower price ranges.I buy only 10mm or thicker(not counting any attached underlay), and no wider than 4".

If he plans to survive in the business he needs to grow thicker skin. 

If, like many houses, that crack has been there like forever and hasn't gotten any deeper/thicker than like an eighth of an inch, run down to your local home improvement store, buy a small container of wall patch, sand paper, a putty knife, some matching paint and a paintbrush.

I look at a few things with this: 1) Do I want to learn2) What is the cost of the added work3) Will one of the options look out of place#3 is up for debate but IMO, if you have short baseboard (3.25” standard) and you add a quality underpayment and thicker LVP, once you add your qtr round you could easily loose 20% of the height of your baseboard.

It was a lot thicker but we figured it would be ok.

It's over a 100 acre property with a good aquifer below it.In Arizona we've had good success with Italian, Greek, Spanish, and some Rhone varietals, thicker skinned reds particularly.

These are thicker and will fill small gaps and prevent additional damage from water, at least for a while.Rather than put a band-aid on it, you may just consider replacing the deck. 

The "thicker stuff"...  5mm or greater product thickness.Any thoughts / recommendations /input?  

If I recall correctly, it was a thicker slab of granite than Home Depot or Lowes and also at a cheaper price point (installed) because we chose one of those 'leftover' slabs.You can find great deals from any of those locations though, so shop around and keep in mind to inquire about the unused leftover slabs from previous installations.  

Buyers can't see 2x6 walls, upgraded insulation, thicker t&g subfloors, 3/4" plumbing trunk lines, etc.