How old was Hashirama when Konoha was founded?

– izuna was 24 when he died, so given that madara is older and it didn’t seem like much time passed between his death and the truce between the uchiha and the senju, Madara and Hashirama were probably 27-30ish when the village was founded.

Who founded Konoha?

The Uchiha and Senju founded Konohagakure. During the Warring States Period, the ninja was organized into small mercenary clans that knew nothing but battle. The two strongest of these clans were the Senju and the Uchiha, who had warred against each other for their entire histories.