For US citizens, be really careful with freelancing overseas. You will probably need to file US self-employment tax statements quarterly, and face some scary penalties if you forget.
Another thing to know is that the US imposes worldwide reporting requirements on banking institutions for their US citizen customers. This problem is far less severe than it initially was, but depending where you go some banks/institutions may deny or restrict your access to financial products because they don't want to deal with the reporting requirements attached to you. Again, it's probably fine anywhere in Europe (nowadays anyway), but elsewhere in the world it may be extremely difficult to do something as simple as get a simple checking account.
https://brighttax.com/blog/expats-self-employment-tax-foreig...