If he's getting into the vape scene whats he looking to do? A shop, web store, through facebook/forums? He looking at starter kits, mods, e-liquids? (Yeah I'm nosey) Plenty on here have experience with one or more of these and the more we know the more we can try to help, finding a niche is key to a profitable business.
E.g. In regards to liquids there's a lot out there so something different (custo made, good price or flavour etc) or imported from the US ones are usually popular
Mods are a tricky business cause your competing with online prices (and clones) and theres a large selection so what to get in, how many etc.
Accessories / custom stuff now theres not a lot out there you can just walk in and buy easily (different drip tips (long churchwarden style) pipe mods (yeah i want a gandalf vape pipe so im gonna keep mentioning it
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I think a 'My First RBA/RDA kit' would be good, have a set with wire, clippers, pliers, cotton/silica, something to wrap around (multiple sizes) etc. that is everything someone would need to start making their own coils, very few places do an actual kit for that you kind of just have to watch vids or wing it with what you have in the house (i got an old nail set with clippers and tweezers and used toothpicks for my first few then i bought some better stuff)
Replacement parts, oh god how nice it would be to pop into a shop and get a new firing pin for a nemesis or that little bloody pin to stop the button from slipping.
Your are on a site with people who are wanting this kind of thing, its basically first hand market research so ask us and then weigh up the options