Read up on outdated and recalled electrical panel identification, some of the old panels are uninsurable.

I bought the house that needed a new roof, water heater and some electrical panel upgrades.

I would have moved in right away to live in while we fixed it up (decent condition paint, flooring) but we have a baby and we got a homestyle mortgage rehab loan and are spending 70k putting in solid hardwood floors throughout (was carpet or vinyl sheets), painting grey (was yellow/beige), new hvac system, (furnace worked but ac needed repair, both systems 15 years old), new hot water heater, new trendy white kitchen (15k with granite) with wood look tile, new electrical panel, etc.

Needs:Cabinets/countertops All appliances in kitchenTile in kitchen Wiring brought up to codeFans/fixtures in every room Asbestos tile removal  Carpet in rooms laminate in living room hallways Central air (furnace brand new)Paint/Baseboard replacement Minor Sheetrock work New roof soffits/guttersoutlets replacedpannel rewiring (the house was built in the early 60's)windowsbedroom doorspaintwood panel remove in two bedrooms with no sheetrock behind it small not load bearing wall demo  I know This is asking for a lot but I really don't know and I know numbers make or break a deal.

If you can do that instead, unit A is paying directly way earlier.Around here going from 2 units to 3 units on a given meter would likely require a new entrance cable and shutoff or breaker panel, unless that meter has a lot of unused amperage. 

Why not just ditch the boiler and upgrade your panel and have an electric furnace installed? 

@Everest Jordan, I recently listened to an expert panel discussion with James Eng, Dino Pierce, Jonathan Twombly and Jeremy Roll.They had some interesting things to say from a macro point of view.James, Jonathan, and Jeremy were certainly advising caution.For example, James Eng mentioned that he looks at dozens of T12's every day and what he is noticing is that the rents are flat, so at the moment there is no ability to drive rent growth.This tells him that the market is definitely softening.

Check out your utility panel to see if it's new or has to be replaced.

Thankfully we had moved the electrical panel to the back porch a year earlier when we rewired & eliminated the old 'screw you' fuses.I fired off a text to my maintenance guy & he was there by 5am as it took that long for the fire dept. to pump out her basement.

4) Electrical - Main Panel size/number of breaker slots/wire size/grounded?