Offer your thoughts or opinion on the input financial query or topic using your financial background.

What is a rule of thumb for accruing debt on a rental property?
To start, I hope you are aware that the properties' basis gets stepped up to market value on inheritance.  The new basis is the start for the depreciation that must be applied each year after being placed in service as rental units. This is not optional. Upon selling the units, depreciation is recaptured whether it's taken each year or not. There is no rule of thumb for such matters. Some owners would simply collect the rent, keep a reserve for expenses or empty units, and pocket the difference. Others would refinance to take cash out and leverage to buy more property. The banker is not your friend, by the way. He is a salesman looking to get his cut. The market has had a good recent run, doubling from its lows. Right now, I'm not rushing to prepay my 3.5% mortgage sooner than it's due, nor am I looking to pull out $500K to throw into the market.  Your proposal may very well work if the market sees a return higher than the mortgage rate. On the flip side I'm compelled to ask - if the market drops 40% right after you buy in, will you lose sleep?  And a fellow poster (@littleadv) is whispering to me - ask a pro if the tax on a rental mortgage is still deductible when used for other purposes, e.g. a stock purchase unrelated to the properties.   Last, there are those who suggest that if you want to keep investing in real estate, leverage is fine as long as the numbers work. From the scenario you described, you plan to leverage into an already pretty high (in terms of PE10) and simply magnifying your risk.