question closely, examine in detail

I look into the costs.

私は費用を調べます

I look into the costs before signing.

私は契約の前に費用を調べます

I look into the costs in the office before signing.

私は契約の前に事務所で費用を調べます

I look into the costs with the person in charge in the office before signing.

私は契約の前に事務所で担当者と費用を調べます

I look into the costs item by item with the person in charge in the office before signing.

私は契約の前に事務所で担当者と費用を項目別に調べます