As late as 1368, the castellans of his castles and representatives of the cities of Horn, Detmold and Blomberg published a joint declaration, stating that in the future, they would only recognize the heir as their sovereign only if the two main cities in the Lordship, Lippstadt and Lemgo, would agree.
In the ancestral lands around the cities of Lippstadt and Rheda, however, the situation was complicated, because after the death of his uncle Bernard V, around 1365, his widow Richarda had initially given his part of Lippe to Count Otto VI of Tecklenburg, who was the husband of her eldest daughter.
He ended up having to pledge half of Lippstadt in 1376 to the relatives of his mother, the House of La Marck.
Around 1400, the cities of Barntrup and Salzuflen and Sternberg Castle were pledged to Simon III.
In 1403, Simon III agreed a treaty of inheritance with the childless Count Herman VII of Everstein.