The rental income would be a major benefit. Apply that towards the principal every month, and you'd make some headway. None of the calc's below factor in that money.
You will pay much more than 6% to sell if you use a realtor. We lost about 10% of the final cost in our recent sale through additional nickel and diming without having to make any repairs. The realtor doesn't even have the best deal at the end-they at least do something that contributes to the sale. You'll be paying other percentage based fees to entities or agencies you've never seen or talked to during the sale process, and you might have to make repairs too.
Regarding your rent--during the early stages of a 30 year mortgage you are largely paying interest. In five years of a $725k mortgage at a 4.5% rate, you'd pay $220k just for the mortgage ($3675/month, not including insurance, PMI and taxes--you're well above $3675 when you include all those extras). You'd buy $65k off the principal, meaning you owe $660k if you sell at that point. You're paying $155k in interest that's out the window just like the rent (minus the almighty tax deductions). If you sold at that point for $775k, you'd have around $700k left after paying the ~10% in fees. You pay $660k to the bank and you've lost around $10k on your $50k downpayment. You also got some tax deduction benefits, but you also paid property taxes, PMI and some repair bills. (Double check all that math, because I did it quickly using an amortization table off the net).
Bottom line: I think you lose money if you sell at the same price in 5 years because almost all of the transaction fees are built into the seller's side. You could also win huge if the market spikes. You could also win huge due to the rental money. You could also have to evict a tenant and pay huge repair bills. It's simply a gamble if you're in it to make money.
http://www.nytimes.com/interactive/business/buy-rent-calculator.html?_r=0http://www.closingonyourhome.com/house-closing/house-selling-costs/Again, I'm not trying to dissuade you, just hoping you consider all the costs (and the true ones at that). You might not hear them from the real estate agent. You are going to pay good money for a place to live for the rest of your life, and I would say that money shouldn't be the only factor in those decisions. There is no free lunch or EZ MONEY to be made unless you get lucky or work very hard to know the market. There are certainly deals to be had, but you can easily be the sucker in those deals.