Hi-Hope someone can help me!

I recently closed on a rental property. It is a duplex with one 65 gal hot water heater that is shared between the 2 units.

Tenant 1 was complaining he had no hot water. Come to find out (after closing) that the breaker for the hot water heater is in tenant 2 electrical panel. Seems as though tenant 2 flips the breaker off.

I want to install a tank less tank in tenant 1 unit. They will still share the water. They do not share the electricity.

Can this be done???

Looking forward to suggestions!!