I need some advice. My landlord has recently closed the business he had in his basement. This business and the home he purchased in the 60's. Each have it's own meters and breaker panels. He was told that a few ceiling lights in the residence were on the business panel, so he asked if they could be moved to the residential panel when he disconnects the business service. I found a real mess. Most of the entire building is on the business panel and the remaining were on the the other panel. That panel, even though it has it's own meter, has NO MAIN BREAKER. There is my dilemma. So, about half of the business panel load will go away when I remove the business circuits. I want to have the service disconnected on the NO MAIN panel and treat it as a sub-panel. That way the whole structure is on one service. The total load will be within the allowable load for the "business" panel's service. That's a mouthful. Setting aside each municipal code requirements, would this generally be allowable considering the situation?

I want to run THHN 8 AWG 40 amp circuit and THHN 12 AWG 20 amp circuit in the same 3/4 pipe can this happen?