Initially he worked in his father's shop at one end of the main market place in Swinemünde, then successfully completing his apprenticeship at the Drugs Wholesaler operated by Theodor Pée at nearby Stettin.

[3] He then worked successively as a commercial representative for a pharmaceuticals company, the advertising manager of a publishing firm and then, in Heilbronn, as the editor-in-chief of a specialist journal.

He was also a great lover of nature, deeply interested in mushrooms and toadstools, and an active member of the International Organisation of Good Templars.

In 1920 he published his book "Aus Armut zum Wohlstand" ("From Poverty to Prosperity") in which he first set down his proposals for a form of savings institution to support house building.

As the currency began to stabilise, on 16 February 1924 a meeting took place at the "Silbener Hecht" ("Silver Pike") alcohol-free restaurant in Stuttgart.

Kropp was able to persuade Mathilde Planck, Robert Ankele and other sceptical members of his plans for a relaunch of the "Bausparkasse" ("Building savings bank"), this time to be backed by a news publication.

As soon as the savings for a year group reached a predetermined level, it would be determined through a form of annual lottery which savers should be entitled to receive their house loan.

The loan interest rate would initially be set at 7% but it would gradually be lowered to 5% as the outstanding balance was reduced.

This time the founders agreed to convert their GdF into a limited liability entity (though it is not clear from sources whether this was done in 1924 or only a few years later).

The first investor was a senior railway inspector, Johannes Rau, the Heidenheim station master, who joined up on 7 April 1924.

The third largest group, representing 16%, consisted of workers and commercial employees – probably including salesmen.

The self employed represented 12% These included doctors, businessmen, pharmacists, artists, journalists and master builders.

In 1925 he took a step back, resigning his post as CEO and accepting appointment as chair of the supervisory board ("Aufsichtsrat").