Great Post, great info. I share the philosophy of Nathan Click. I have recently been in the same situation as you where I have 3 free and clear rentals. The reason being is that I made "power buys" in cash to squeeze better deals.
6 months down the road and here I am with these 3 units earning a 7.5%-9.5% ROI on my money. Not bad, but when I calculate the ROI on leveraging, I'm forecasting 20%-25%. In addition, I will have twice as many properties to DEPRECIATE.
Trust yourself, and make this move IF you are buying the next property right. I shopped pretty hard on my Refi and found 3 main products....5/1 ARM (lock at 4.25% for 5 years, then review, $2500 origination) Interest only (wasn't interested as it didn't align w my longterm goals), and a Fixed Product (15-30 yrs. high origination costs). I chose the 30 yr fixed with the high origination costs because It allows me to calculate exact cash flows, ROIs, and I think I will sleep easier at night knowing exactly what the payments will be. The 30 yr fixed is for the long term investor as the origination costs are very high. If you see yourself selling in 2-5 yrs, take a shot at locking the 5/1 Arm at roughly 4.5% and $2500 origination.