Is it dangerous? I backpacked Europe before, but only got as far east as Prague. Does it get sketchy further east? I'm considering starting in Athens or Istanbul and then heading north to Poland through Bulgaria, Romania, Serbia, Hungary, and Slovakia.
Business in Athens and Sofia (Bulgaria) is a good starting place. Lots of inspiring people, especially in Athens.
Bulgaria and Romania is too much corrupted for business so, be careful.
Athens have some strikes every 30 days so read newspaper to know what is working and what is not (I am referring public transportation, airport, public sector services, etc).
If you go to for fun, are you out of your mind? You go this time of year, when the party starts in 2 months in these countries. Think again.
That's my 2 cents.