The question is why is he becoming a collector? Is it to make money over time as gun values increase? Is it as a hobby and he is going to shoot his collection? Those answers will tell you which direction to go.
If you are looking for guns as a investment stop and don't waste your time and money. The chances of making major profits that way are near lottery odds. Doubles in all but the higher grades have been a flat or declining investment for several years and I don't see that trend changing. Just how many old men are coming along who want to shoot or hunt with Sid by sees? Fewer each year. Low grade guns can be bought for the same or lesser prices than they bought 8-10 years ago.
Rare and high grade guns will command good prices still and should in the future but there are no guarantees. Antique China commanded higher prices in the past and friends in the business tell me they are stuck with a lot of nice rare China with almost no on interested in buying it. The next generation are sellers of stuff not buyers like my generation has been. Simple supply and demand.
If you like to shoot, pick a brand you like and buy the highest condition examples you can find and treat them kindly while shooting them. Or collect examples of some feature like different locking or opening systems. These are fascinating mechanical devices which show endless creative examples of design and improvement as well as dead end designs.
