Two London-based companies are among those who have already taken the plunge. Their experience highlights the attractions of the German capital but also the bureaucracy that lurks behind the marketing, a factor in the global tussle for business unleashed by the Brexit vote.
Web-design company MBJ London and real-estate investment platform Brickvest, both co-run by Germans, had already planned to open offices in Berlin but were jolted into speeding up their investments by Britons' June 23 decision.
The motivation: to limit their London exposure in case of a "hard Brexit" - where Britain loses access to the single market.
The two firms cite access to talent and the low cost of living among Berlin's benefits, as well as a hotline to help start-ups get employee visas.
But they urged the city to lower language and regulatory hurdles and offer more flexible office space.
"If it wants to become the leader in fintech then these are the steps it needs to take, otherwise it will get a few companies but it will not become the hub," said Brickvest co-founder Thomas Schneider.
Brickvest is building a back office in Berlin and plans to grow its staff from five to 15 people over the next six months. A "hard Brexit" would make London just a small regional office.
But Schneider said the German financial regulator BaFin was too conservative and the fact that all documents must be translated into German to apply for a banking licence was off-putting for companies like his, which employs 10 nationalities.
As a result, Brickvest is more likely to apply for a licence in Ireland's capital Dublin - and open a front office there - if Britain loses its passporting rights - the ability under EU rules for any financial firm to serve the whole region from a single base.
BaFin acknowledged documents must be submitted in German for banking licences but said this was not always necessary in other areas, such as insurance.
"BaFin is, however, continually addressing developments around Brexit, both from a legal and regulatory perspective. The same applies to applications from Fintech companies," it said in a statement.