A number of changes are taking place at the borders -- some gradually, some immediately. And small-scale border trading, the only livelihood for many impoverished residents of Ukraine and Belarus, is likely to be strongly scaled back.
But with the borders of those countries now regulated by the EU's visa regimes, such cross-border trade has already sharply declined.
A majority of the trade takes place along the Ukrainian Polish border. Oksana Plyak is a pensioner living in the small western Ukrainian village of Bikiv near the Polish border. She tells Reuters that with pensions of only about $20 per month, many people are surviving thanks only to border trade.
Poland's stricter border control has already scared off many traders. Plyak continues to trade, but it's not an easy day's work. She has to walk 7 kilometers and spend three or four hours waiting in line for a visa that allows her to cross into Poland for the day.
Plyak is worried the EU expansion will mean the end of her extra income, even though the payoff is next to nothing.
"And from all of this you won't make more than three to four dollars a crossing because you can't carry that many [things to sell]. You can make more money, but I don't know if I can carry any more."
Belarusians living in the border regions with Poland, Latvia, and Lithuania are also afraid they will be affected by the new regulations.
Andrei Fedorov is an independent political analyst in Minsk. He says the regulations being imposed by each of the border countries have slight differences.
"As concerns Poland, as far as I know, a visa will become twice as cheap. From the first of May, a one-time visa will cost 5 euros [$6], but I think it is not even connected with the [Polish] EU accession because the agreement was reached earlier. As concerns Latvia, it will introduce a substantially more expensive visa -- from 10 to 25 euros. However, instead of several types of visas there will be only two types of visas left -- a transit visa and a visa for entering the country," Fedorov says.
Few border traders can afford to pay 25 or even 10 euros for a visa. Even Poland's 5 euro visa will dip heavily into whatever profits a cross-border trader can hope to make in a day's work.
Sergio Carrera is a political analyst with the Center for European Policy Studies in Brussels, where he specializes in EU visa policy and free-movement issues. He says the European Commission has repeatedly said the new border regimes should not become a barrier to trade or cultural exchange, and has taken steps to facilitate local border traffic.
"It will grant a specific sort of visa for people living in an area close to the border, within 50 kilometers. And this visa will allow people traveling to Poland -- for instance, for purposes of trade or for purposes of family, with those people who are living very close to the Polish border and have family in Poland -- they will have the possibility by holding this visa to come in and come out of Poland without the necessity of further administrative checks and lengthy procedures," Carrera says.
Carrera also says that cross-border trade and traveling within the new EU countries will inevitably become more complicated for Belarusians and Ukrainians after the new members become full-fledged members of the Schengen agreement in three years.
Carrera says technically, Germany's eastern border will remain the official EU border for that time. Until the new members fully join Schengen, the EU will have two eastern borders rather than one.