Cash and the mechanics of cash transactions:
This means hard local currency. In scenario zero through scenario three, this will usually mean U.S. dollars, Canadian dollars, the currency of a local stable government (do not use pesos). Obviously, cash is often the surest and fastest way to buy almost anything an honest face to face transaction. Cash purchases usually are convenient for both the buyer and the seller, but usually more for the seller. Many sellers refuse to do business any other way. These sellers who have negotiable prices are usually more willing to lower a price for a cash customer than persons who pay by other means are.
Cash is also a medium of exchange that is unfortunately a common object of theft and robbery. For that reason, it is important to utilize a higher degree of physical security when dealing with larger cash transactions. It is common and often expected that those who conduct large cash transactions travel armed. What constitutes a "large" cash transaction is somewhat determined by the place and people you are dealing with. In affluent places, that is anything over $10,000 but in most normal places, it would be for anything significantly over $1,000. Another determiner on this is the class of the people involved as many people will not travel unarmed with an amount of cash that would be worth fighting for. IE this can be up to $3,000 for fairly hip players, but as low as $200 for a low wage earner. There are some people who will travel with $20K in cash unarmed with little or no security, but that is very very rare since most of the world's wealthy travel with various debit and credit cards and not much cash. The level of armament is usually in direct correlation to the risk of the individuals involved and the amount of cash involved. If someone goes into a deal with an inordinate amount of protection, then their actions may be taken as a precursor to robbery or them being too paranoid and the fear of the other party taken as a sign of disrespect. On that notion, those who have an established place of business have the right to expect patrons to come unarmed when conducting normal transactions. This includes gun dealers who deal out of their homes. Moreover, it is the person who goes unarmed to a cash deal who is showing the greatest amount of respect, but this should be approached wisely.
Most conventional wisdom is to keep cash hidden and guarded, but when your intent is to do business, you have to do what is necessary to make it very clear you are capable of quickly covering the deal which means "flashing" money when it will get the message across. Fancy cars, clothes and jewelry can be borrowed, faked or stolen, so they play less of a role in determining the seriousness of a gun buyer than the actual cash. Among gun collectors though, if you are known to own other guns in a certain class, the dealers and other collectors will often feel more relaxed about showing you guns in a similar class. This can often reach such a point of trust that dealers and collectors will extend credit and give merchandise on the promise of a favorable trade at a later date.
Many black market and gray market gun dealers will refuse to even talk seriously with a potential buyer unless they or a trusted intermediary are physically shown at least enough cash to cover the proposed purchase. Obviously there is a limit to how much cash it is wise to show if you are utilizing the "this is all the money I have on me" method of negotiation. A so-called potential customer who wants to look at merchandise without showing or determining the means of payment will often not be taken seriously, or worse, be considered a potential thief or robber who is trying to get the dealer to tip his hand and disclose potential loot. This is when it can be important to show a wad of cash in the company of those who will be in contact with those who you will be buying from, or the dealer himself. Persons who are not accustomed to cash deals where one or both parties go armed will probably be fearful of doing business with someone who comes on too heavy, so one must be careful in how the cash is presented.
In my experience, the larger denomination bills the better. It saves counting time and space in the wallet or envelope. Low level drug peddlers and strippers do business with large amounts of small bills, not gun dealers. Also separate the money by bill size and amounts. Example, fives, tens and twenties can go in the wallet, ones in a pocket, and hundreds should be tucked away in an envelope or second wallet or money clip. What can leads to problems in counting money or giving someone time to consider renegotiation is large amounts of small bills. Counting $1,500 in $20 bills might make you feel like a rich player, but in reality it is a tedious activity that can lead to disagreements over miscounting and potential hazards of mixing counterfeit bills or simply having too much money on hand to quickly deal with. In these circumstances should they happen, the money should be organized in pre-counted bundles that can be spot checked. Again, if you are dealing with guns in cash, you want the deal to go fairly quickly, then get your merchandise out of the AO. If you want to chat and visit, save that for when the deal is done. One little kicker that can be a fly in the soup is that government agents often think the same way, learning their trade from the dealers they bust or turn informant. The government agent will usually know "too much" about making a cash deal working smoothly, while Joe Sixpack who gets his money from an ATM gets piles of twenties and can have difficulty getting larger numbers of big bills.
One aspect of timing on cash transactions is that they are usually considered final upon completion with the seller holding the obligation to satisfy the buyer. While someone might want to consider a trade deal not closed until both parties are satisfied with the goods, cash is always assumed to be satisfactory, thus the buyer is the only one with the right to renege on the deal on the basis of it being unsatisfactory as would be in the case of defective or damaged merchandise where such defects were not disclosed prior to the sale. So, if you want to buy something and make sure you will be able to force the seller to stick to the bargain, it is generally accepted that you will achieve this when you pay promptly in cash.