Proof of funds for Aufenthaltstitel zur Arbeitsplatzsuche

Hallo,

My 18d residence permit will end in the autumn and, according to the Aufenthaltsgesetz § 20, I may apply for a Befristeter Aufenthaltstitel zur Beschäftigung with up to 18 months' validity. My wife and child will also require new residence permits and their applications will be included with mine. (see, https://service.berlin.de/dienstleistung/324661/)

My question is twofold: How much proof of funds must we show when applying? And, does this amount take into account the number of applicants (three from the same family)?

Vielen Dank im Voraus,

Dr Meral