Renovating a leased 4-unit -- strategy?

[Christian Carson]

Our offer on a 4-unit brick walk-up 2-story building was just accepted. It's fully leased (month-to month, below market rents.) I would like to renovate this building, specifically in this order:

1. Delete steam heat and add new forced-air and A/C (have quote).

2. Redo electrical in basement, relocating all boxes to a single location in front basement.

3. Add two basement units in currently unfinished basement (they are already firewalled with two exits each). I can't do this until all units have new HVAC because I will have to remove the boiler completely to make room for the basement units.

4. Renovate ("freshen") the upstairs units.

The problem is I don't know when or how to go about accomplishing this since there are already tenants in the upstairs units. The prime rental season is in May/June with many single graduate students from the university about a mile away looking for apartments.

The tenants are month-to-month and their rents are below market. Should I just terminate their leases and do all the renovations at once, ready to rent in May? Should I allow the tenants to stay while the HVAC is installed, then raise their rent in May?

I'm looking at about a $350 - $400/mo per-unit bump in rent after the renovation, which includes shifting the gas bill from landlord to tenant. I would like to have these all done at once but I also don't want to interrupt my cash flow, though I can survive if we don't rent.

What do you guys think?