Two units and a pool pump? So the $600 is partially your tenants responsibility- or are the 'kids' living in the other unit? If they are old enough to live in the unit they are old enough to pay some kind of rent! Check your pool pump rating - a variable speed pump will save you money after an initial outlay of about $2K. ( About $10.00/mo @ 10 hrs daily run time v $50/mo for 6 hrs run time with a single speed) Even if you put the pool pump on a credit card you would break even by applying the savings on electricity to your credit card payment until the pump was paid off!