New windows for rental? Worth it for more rent?

[Jeff T.]

My tenant would like me to put in new windows. The windows are currently louvered windows (6 inch wide), basically the leakiest possible windows, which was great before air conditioning, but not great now. Anyhow, tenants AC bill is really high in the summer. They are willing to pay more for rent also. They are good tenants. So for $4500-5500 I can replace the windows. I can probably get $50-75 a month more when I replace them. Anyone have thoughts on whether I should do this? I will probably use my HELOC to pay for the windows at 4% adjustable. Thanks!