Exactly, although I would personally be more likely to put the money in bonds or cash instruments—something with less volatility than the stock market. Think of it this way: You wouldn’t take out a $300K loan at 6% and put it in the stock market, would you?
If you can find an investment that pays about the same as the interest rate you are paying (pretty feasible in the 30-year window of a traditional mortgage), then you’ll actually make (your marginal tax rate) x (interest paid) a year out of the tax writeoff.
Except (and most people overlook this), you shouldn’t consider the effective rate of your mortgage in a vacuum, you should take into account the standard deduction. Few people without a mortgage itemize deductions. If you are paying $12,000 in deductable interest a year, and the standard deduction is $5,000, all of a sudden you’re only making (marginal tax rate) x (interest paid - standard deduction) a year.
Why are you counting the loan PLUS rent? I think it’s because you would own one house, but have to live somewhere else. If so, your math is wrong, for a couple reasons.
First, if you’re going to be living in Austin before moving to NE, then wait to buy the house until you’re actually ready to move. As others have pointed out, we’re in a falling market, so you may stand to gain from waiting simply because of that.
Second, if you’re going to be paying rent to live somewhere other than the house you buy, that will cost you regardless of whether you buy with cash or use a mortgage. You can’t count the rent against your hypothetical mortgage-case cashflow, but not against your cash-case cashflow and expect to get valid results.
The cashflow you should be balancing are the cost of the mortgage (with all applicable tax benefits) vs the interest you can earn on the money in other investments. Your individual finances will apply, but given the mortgage tax deduction, it is very likely that a mortgage is in your best interest. The deck is simply stacked towards homeowners with mortgages.
I agree with the others who told you to seek the advice of a professional financial advisor. Get one that you pay by the hour, not one who makes a commission on the products he sells you.
And, now, my personal recommendation*. Don’t buy a house. You’re going to have an uncertain living condition for the next several years, you will likely lose money if you have to rent out a house in the short term, and the transaction costs for housing are high compared to other investments. It sounds to me like you’ve got the idea that housing is a rock-solid, high yeild, low-risk investment, and since you’ve got a bunch of money coming in, there’s no better place to put it than a house. It’s an easy impression to get from the market in the last couple of years, but it’s not well-supported by historical trends.
*advice freely given on the internet is worth what you pay for it, avoid direct sunlight, do not operate heavy machinery or go swimming for at least 30 minutes after reading this advice