One of my houses has 4 bedrooms but we only use 2 as sleeping rooms so as to discourage the larger party groups (we made the others a yoga room and an office). 

Both do NOT have HVAC, only module heating units.

I asked the tenant reasons why he wanted it and not so much of light but heat from the sun.

I have experience opening and managing aerial/dance/&yoga studios and there is a local teacher who is looking to grow her business who I want to support and see succeed.

What kind of heating usually you guys provide the tenant .Also septic tank seems common , so when buying a place are you guy doing a separate inspection of that or that is covered by city/County

If the concern is that they're "paying to heat/cool common space" that's not the case.

So I'm thinking of setting a fixed monthly surcharge for heat and hot water, plus a charge for the 'free' laundry I provide.

I explain they are free to live in the apartment or live elsewhere for the duration of the lease, but it is their responsibility to pay the rent and maintain heat in the apartment as per the terms of the lease.I also explain that circumstances change and I am human.

It comes with 3 water heaters, 3 separate electric panels, however landlord pays for heat since there is only 1 furnace.

Adding a heating and cooling system (the reason this house was not operational), and minor interior renovations.