Is it legal to buy concurrency in USA I would like to seek for your help since I would like to have confident answers on the following questions:
(please include links for official websites)


Is it legal to buy &amp; hold currencies (such as ripple, bitcoin,etc..) as a kind of investment in the USA?
When do you have to tax after it?
Do you have to report is on your tax form even before you sell it or only after you sold the currencies?


So far this is what I found:
https://www.irs.gov/pub/irs-drop/n-14-21.pdf
Yes.  It is legal to buy cryptocurrencies in the USA and they are taxed like property by the IRS.

See https://en.wikipedia.org/wiki/Legality_of_bitcoin_by_country_or_territory#North_America

From the WIKI:


  The U.S. Treasury classified bitcoin as a convertible decentralized
  virtual currency in 2013.[26] The Commodity Futures Trading
  Commission, CFTC, classified bitcoin as a commodity in September 2015.
  Per IRS, bitcoin is taxed as a property.[27]
  
  In September 2016, a federal judge ruled that "Bitcoins are funds
  within the plain meaning of that term".[28]
  
  [26] "Statement of Jennifer Shasky Calvery, Director Financial Crimes
  Enforcement Network United States Department of the Treasury Before
  the United States Senate Committee on Banking, Housing, and Urban
  Affairs Subcommittee on National Security and International Trade and
  Finance Subcommittee on Economic Policy". fincen.gov. Financial Crimes
  Enforcement Network. 19 November 2013. Retrieved 1 June 2014.
  
  [27] "IRS Virtual Currency Guidance : Virtual Currency Is Treated as
  Property for U.S. Federal Tax Purposes; General Rules for Property
  Transactions Apply". www.irs.gov. Retrieved 2017-04-22.
  
  [28]
  https://www.reuters.com/article/us-jpmorgan-cyber-bitcoin-idUSKCN11P2DE