ballpark figure for replacing knob and tube wiring
I do a lot of these old houses 1-3 full rewires and 3-5 partial rewires a year and I can tell you that for budgeting purposes I figure between $12 and $16 per square foot for knob and tube rewire depending on the level of foreseeable difficulty. Houses that have conduit systems are between $6 and $10 per square foot for budgeting! Included in the budget is the main electrical service and panel/s, all new wiring and new standard devices, also includes adding new outlets to meet current codes in kitchens, baths and throughout house and installation of smoke detectors. It does not include fixtures!
AFCI's are now required for almost everything so that will add a couple hundred bucks to each unit.
I am in Miami and most of these homes are in Coral Gables and I have heard that Miami wages and costs for materials is higher than a lot of other states so ask a contractor local to you.
I don't give firm prices to do this type of work and have worked the square foot budget from the many I have completed. The jobs are done on a time and material basis and I am usually pretty close with my budgets.
Being multi story makes it more difficult than single story and being multi unit means (4) services and (4) panels so I would probably calculate the units separately and use the higher price to get you a budget
Answers based on the mood I am in when you ask!