Where can you purchase old Russian and American submarines?

American submarines are not for sale. Most older ones were either scrapped or are museums (Arkansas even has one). Some older diesel-electric boats are transferred to foreign nations, but the nuclear ones never escape government control, even when dismantled.

Russian submarines are mothballed in Russian harbors, and with enough money, the right connections, and plenty of patience you might manage to buy one. Don't get any ideas of terrorizing the Seven Seas though, any Russian sub you buy will be a noisy, slow, unreliable diesel-electric boat. There's a couple in California, one in Long Beach near the Queen Mary and another in San Diego.