From experience with several small dealers that have built up a sizable / respectable business over the 20 years.
Rega
Rotel
Audio Research
B&W
Pass
McIntosh
Sonus Faber
luxman
DynAudio
Nordost
Cardas
Most of these brands are not available to just anyone, they have only one retailer covering a territory. You must prove yourself to them, that you have integrity, provide great support, and have volumes to justify their giving you the territory. It takes years to develop a retail outlet of high end brands.
It also takes money. Often you have to purchase upfront lots of product. So as a part of developing a store you need to develop a cash flow to support purchases in advance of sales.
One of the real keys to success is to have it in stock… the sale if a $10K component is having it in stock. So, success can be contingent on carrying half a million or more of inventory.
My friend has higher level brands… but it took years to get them. Companies like Boulder, TechDAS, Linn… they don’t just sell to anyone. You have to prove you are worthy… I am not kidding… this takes work.
He better be willing to work his butt off… to be passionate about what he is doing and willing to invest 70 hours a week for the next ten years to get going.