So, what do you do? Obviously, you can hold for a year or longer. But then you lose the quick return that a flip provides. So...
Search out a good mortgage broker. Find one who works with lenders who will lend to a buyer of a rehabbed property. You want to do that for several reasons. First, you want to know what's out there and what's available. You'll also want to tell your buyer that. And, really most important, you want to remain in control. You don't want to buy a property, rehab it, market it, and then have the buyer botch the transaction because he/she has gone to his/her local bank, and that local bank is afraid to do the loan. Stay in control.
Second technique (though I'd really stick with the first one, above; I just present this to show that there are a couple of different ways to make this work): Buy the property. Then create an Illinois-style land trust. It can be called whatever you like, though it's nice if you identify it by the address--i.e., 123 Main Street Land Trust. Move the property into the trust. The mortgage will still be in your name, and there's no due on sale clause applicable (it's an exemption in the Garn St. Germain Act). So, the mortgage is in your name, but ownership of the actual property is now vested with the trust's trustee. And the real estate--the property--is now within an item of personal property (personalty)--the trust.
You sell a portion (up to 90%...you must retain some ownership of the trust in order to avoid triggering the due on sale clause) to the property's buyer. The property's buyer also signs a residency agreement--somewhat similar to a lease--with the trust, thereby leasing the property from the trust. And another document specifies that, after a specified period of time, the property will be brought out of the trust and the "buyer" will have first rights to purchase the property. Every month, the "buyer," the resident beneficiary of the trust, makes his monthly payments to the Trustee, who then pays the mortgage. At some point, a year or two later depending on what you've agreed to, the property is brought out of the trust, the buyer buys the property, and the deal is concluded.
Using a land trust seasons your mortgage. It's remained in your name for the year or two until property is brought out of the trust and sold to him. You won't be able to get all of your money out at inception, but--somewhat similar to a lease-option--the buyer will provide an option fee at inception. The option fee is negotiable, but you might make it similar to what a person would provide as a down payment, if he were purchasing the property--i.e., 5% or 10%, or even more.
I've also heard of people putting the property into an LLC to address the seasoning issue and for asset protection. However, I'm more familiar and comfortable with land trusts. Still, that's another option to consider.
But my first recommendation would be to find lenders with programs that will allow a buyer to purchase your property without worrying about seasoning. And stay in control of the process.
Hope that helps.
Good luck, I hope you net a profit.