Have just finished a BA (Hons) Business Studies and I began without any prior business studies knowledge. Like you, the management position made it attractive as well as career opportunities.
2 hours a day average is what you're aiming for, and what I did, for the most part. In the first year after B120, I left a gap of 3 months before realising that it would take 6-7 years if that was always the case. After that, I stacked my modules one after the other and upped my yearly average from 60 to around 90, sometimes more if module overlapped. The net result was it took me 4.5 years and freed me up at work and home.
60 points around a full-time job is fine - especially if you'll be having a 2-3 month break before the next module. Also, depending on how you pick it up, you could easily find yourself studying less than the guide of 16 hours per week especially when you get to level 2 and 3 where theories and concepts are repeated in certain areas.
Most important for me was to have an interest and enjoy the topic. When times got tough and had to make sacrifices, it helped that the subject matter was engaging.