What should my priority be?

[Angela Woehl]

Newby here:  I have a duplex which currently clears $400/mo.  I have a $5k available for improvements.  It's in dire need of windows and I've learned that last year (prior to our ownership) the tenants did not use the oil heaters instead opted for electric space heaters.  😲.  Do I lay out for the windows or a mini-split?  If I delay on the mini-split how do I require them to use the oil system?  Do I fill the tanks and charge them which is not in the lease?  Or do I inform them that they have to use the available system which is a financial burden to fill the tank?  Both leases are new 12 months and this issue was not clearly stipulated.   Thanks for the collective wisdom