Once you want to sell your cryptocurrency for fiat, how would you do it?
Would there be any liquidity problems with semi-big sums e.g. 20.000$?
There is a lot of ewallets and exchangers online supporting Bitcoin and other crypto currencies actually. There is no problem usually about exchange in this platforms, especially if you become verified member. For example Coinbase (for some countries) exchange crypto for fiat, also Neteller, and Payza.