The FHA rehab loan is identified as a 203K loan.
The full 203K is known as the standard 203K and is for amounts over $30,000 and/or for properties that require structural repairs. It has a higher rate and more requirements and much stricter underwriting.
The limited 203Ks (the streamline version) is for repairs of $30,000 or less and cannot include any type of structural repair or improvement.
Here is the math for 203K loans: Sales Price + amount needed to do repairs + 10-15% contingency + fees = rehab account.
I am there throughout the process to guide you along.