Why would it not be possible? To my understanding that is pretty much what the EU is about.
> The European Single Market, Internal Market or Common Market is a single market which seeks to guarantee the free movement of goods, capital, services, and labour – the "four freedoms" – within the European Union (EU).
https://en.m.wikipedia.org/wiki/European_Single_Market
> The European Single Market, Internal Market or Common Market is a single market which seeks to guarantee the free movement of goods, capital, services, and labour – the "four freedoms" – within the European Union (EU). https://en.m.wikipedia.org/wiki/European_Single_Market