位 and 立 don't sound similar in modern Mandarin due to historical phonetic changes. They were more similar
in Old Chinese. 位*[ɢ]ʷrəp-s (< *ɢʷəʔ-rəp-s ?) 立*k.rəp
Character Evolution
BronzeLate Western Zhou~800 BCSealWarring States (Chu)475-221 BCSealWarring States (Chu)475-221 BCSealWarring States (Chu)475-221 BCSealShuowen~100 ADClericalWestern Han202 BC-9 ADClericalEastern Han25-220 ADClericalEastern Han25-220 ADClericalEastern Han25-220 ADRegularModern