There are several misconceptions around $2 bills. Many people believe they are no longer produced and haven’t been for many years.
This is false; there are $2 bills that were printed as recently as 2019 and there will be more that are printed when those run out.
Many people believe that they are just collectors’ items and can no longer be spent. That is also false; you can spend them on any purchase at any store. They even work in many vending machines.
Many people also believe that they are almost impossible to find. The truth is that many banks carry them and they probably account for about 0.1% of the paper currency that is circulating around America. They aren’t easy to find and many people do hold onto them rather than spend them, but they are not impossible to find.
There is a seller currently on Etsy selling crisp uncirculated $2 for $6.99. Another is selling 100 crisp uncirculated notes for $299. That’s a $99 profit on a $200 investment, minus shipping cost and commission to the platform you use to sell it (Etsy, Ebay, Amazon, etc.). (It’s probably much easier to sell 100 bills at a time rather than 1 off)
For circulated currency, the premium will be much less, but people will still pay more for a $2 bill than it is worth.
Why do people pay that much? Some people collect and frame the bills almost like a piece of artwork.
Others just like the novelty of spending the bills. For instance, Clemson University football fans historically use $2 bills when they visit an opponent and spend money in that town. It was first used to convince Georgia Tech to schedule them by capturing the attention of local Atlanta business leaders. Now they just do it; sometimes stamping an orange Clemson paw logo on the bill.
Other people just like to get people’s attention or make someone smile. This could be someone tipping a valet or a grandparent handing a $2 bill to their grandchild. Tip with one at a new bar, and they might nail it to the wall as their first customer to use a $2 bill.
The beauty of selling actual currency is that worst case scenario, if you can’t sell your product (money), you can just spend it or deposit it in your bank account.
Compare that to a retailer that buys too much inventory and ends up getting stuck with a bunch of units that no one wants. Maybe they could be liquidated at below their cost, or maybe the retailer gets stuck with them. This would never happen when actual spendable American currency is your product.
The key to selling $2 bills for a profit is finding a good source. You could just look for them circulating around, but your best bet is to go to your bank(s) and ask. If you are a good customer, they might have some you can get from simply withdrawing the equivalent funds from your account. They also might be able to point you in the right direction of how to get more.