hampton - there are two basic approaches to buying guns (or most anything else). One, spend the time to learn enough to know a fair price when you see it. Second, develop a relationship with someone who has spent the time.
For the first approach, leave the wallet home (better yet, make a two year investment) for two years. Read ten books on the gun trade. Visit ten large, specialistit high grade gun dealers. Attend the Las Vegas January show and the Vintage Cup twice. Take a fitting lesson in the USA. Strongly suggested - take a "gun" trip to UK where you visit a big auction, most gunmaker's shops, and take a lesson at one of the shooting grounds.
Or, pick a dealer (hopefully within commuting range), explain what you want for your first gun, become very patient. Be willing to say "No" if your gut says , "No."
Tips: You are much more likely to make a bad deal on an impulsive buy that you are to find a bargain. Decide what you want next, write it down in detail, and review detail before buying. Most likely, there will be no final and "only one more" gun; your tastes and/or needs will change with time and exposure to different guns. Dealers stay in business only because they make money. To make money, the dealer must buy for less than he sells for. If you object to paying for a dealer's expertise, you will have to learn to deal privately on your own.
To start with, the budget owner needs to decide on any country of production restrictions, brand name interest, currnt condition minimums or new only, quality grades to be considered ("A" or "B" grades considered, house best only, extra finish, etc.), new bespoke or "experienced," purpose of the gun (investment, safe queen, clays, upland, live bird, water fowl, historical interest, provenance, etc.), and collection or shooting battery.
Do the above, write it down, review all writing before spending money, and wait a week before any individual purchase. That will be a good start. Hook up with the Carolinas Vintagers in Charlotte for lots of discussion on SxS guns of all description.
