It is within 60 days.From my FHA loan:"Borrower shall occupy, establish, and use the Property as Borrower's principal residence within sixty days after the execution of this Security Instrument (or within sixty days of a later sale or transfer of the Property) and shall continue to occupy..."

You can go to the county Geographic Information System (GIS) or tax assessor websites, depending on size and sophistication of county, and you may find free tools available to search sales by neighborhood or zip code or price range and dates.

On the other hand, property owners benefit greatly by keeping sales data out of the hands of the taxation powers.  

The appraisal took this into account subtracting 15K per sale for an average Adjusted Sale Price of:=$320,347Even though my property was listed as Superior Upgrades along with 3 of the comps.

Sale Price is in the +2.5% range and the houses are in good condition. 

The reasons wholesalers make money are essentially 1) speed to close, and 2) large deferred maintenance that precludes typical sales.

Hence: wholesaling + taking ownership for a bit + full retail end sales price = "wholetailing."

With that said, you technically can refinance any time you want after you close because these conforming loans generally have no prepayment penalty.The other aside that I will mention is that you will want to make sure you have sufficient comparable sales in your area that will be able to document enough value before you spend money on a non refundable appraisal.

@Miho Y.If this is for a conventional loan the all the lender cares about is the sales comparison.  

After improvements are completed I would like to re-sale (flip).