Actual use, past and current business model an practice, correspondence with your professionals, nature and source of the sale, all can be used to demonstrate your intent.If you want to mitigate the pain of having to pay ordinary income + self employment on your flips you could adopt a slower model where you buy rehab rent refi re-evaluate your intent and finally 1031 (someone help me with an acronym for 1031 that begins with "r").  

If your annual household income is $50K you don't bear a huge burden, if it's $250K you won't like that margin tax rate on ordinary income (I'll skip the whole qualified dividend conversation to keep it simple).  

It is usually considered to be ordinary income and may also be subject to Self Employment tax.Second, the taxes on this structure do not vary from state to state.  

Don't confuse that with the "real estate professional" status that would let you offset more ordinary income with passive losses.  

If the suspended losses are in excess of the total gain, the remaining suspended losses will then offset ordinary income.3.

@Josh CorbyYes, @Brenden Mitchum is correct that rental income is treated as ordinary income.

Some will keep late fees, others split them, and some will just take their percent like ordinary rent.

Title companies deal with wholesalers all the time so that's nothing out of the ordinary.  

The formulas they  use is for ordinary Joe's buying their own homes, but totally bogged down when applied to serious investors.I ran into this some years back, in 1993, when interest rates came down from rates of 15% to 7%.

Not doing out of the ordinary.