Maintaining books of accounts for itr 3

Hi. I am an freelance architect. I want to confirm that ITR3 would be applicable to me. Besides this I have income from agriculture & tutoring. My question is, do I need to maintain separate books of accounts for each of these activities? All income & expenditure is linked to my personal bank account , but when we are maintaining books we are maintaining only for business right? so I what would be my cash balance for business? My entire bank balance wont be considered as Bank balance for business