I actually got audited by the IRS on this exact issue. In 2006 I deducted my real estate expenses (seminars, travel to look at deals, legal on the deal I had under contract, etc.) on my Schedule C even though I had not yet closed on my first MHP. But I was actively looking for a deal in good faith, and did have one under contract by the end of 2006. (I did not have my LLC set up in 2006. I just itemized and deducted the expenses.)
When the IRS came calling a few years later, I had all my receipts, which I sent them, and I could document that I actually had under contract by the end of 2006 my first property (which closed in March of 2007). From 2007 onward I could show profits from my MHP (and, of course, that I was paying more in taxes) and that the prior deductions were directly related to subsequently buying that MHP and earning money. (FWIW, I don't think you actually have to have anything under contract - just document that you are making a best efforts to buy real estate and earn money.)
The IRS guy reviewed my receipts, and gave me a clean bill of health. He actually apologized for wasting my time.
Your mileage may vary,