Odds are good the lot was surveyed before you built on it and may even have metal post markers still visible.

After your rehab is complete usually 6-12 months you refinance the home into a conventional loan and if your ARV (After Rehab Value) was high enough you can pull your down payment plus your operating costs out of the built up equity so you essentially purchase the home at no cost. 

This home was built 40 years sgo.

EDIT:  Let me add that I also look at the age of the property, trying to stay with properties built in the late 70s or later to avoid issues with lead base paint and cast iron plumbing.  

@Scott Mac Where'd you get all those pics of the houses I built...?

The was built around 1900. 

The was built around 1900.

They are so very needed and can look just like stick-built with the front-end porches, especially, and are now built to general housing standards. 

This is exactly how we got started and the immense equity we built into that first property has literally paid for all our other investments over time!

My rebuttal to OPM as a small investor (i own one house that im flipping atm) is i haven't built up the contacts to do that with yet.