For a fix and flip you will indeed pay SE tax (social security tax and medicare tax), income tax at your rate, and any state and local taxes. This will be on the $65,000 profit, not on the entire sale amount. The price of the property and your rehab costs are considered the basis, and your holding costs are deductable. Tax will be on the profit, after all expenses, in this (or any other) situation.
As was previously mentioned, if you rent it out for a year or more before selling your profit will get long term capital gains tax treatment, meaning that instead of SE tax plus your regular income bracket tax, you will pay a maximum of 15% in long term capital gains taxes on your profit, and most likely less on some portion of the profit unless you are in a higher income tax bracket (the portion that falls within the 15% or less bracket will not be taxed!).
My advice would be to get some tenants in there and hold it for the year, then if it is still seeming like a big problem to you put it on the market. A fully rented building is more valuable than an empty one in any case. Use incentives if you have to- a month's free rent at the end of a year's lease, reduced security deposit for a lower move in cost, free utilities, whatever it takes to get good renters in there. Better than having the place sit empty! If you sell it now the government is going to take half your profit in taxes.
Of course, if there is no profit then that is not an issue...
Chris