@Tim Kirkland
Welcome to BP! There is no equity requirement. If you purchase a SFD as an investment property, which you can do with as little as 15% down, you can rent it right away. However, when you purchase a property as a primary residence, your Mortgage will include your intention to live in the property for at least one year. If you convert the property to an investment property within the first year, it could trigger the due on sale clause. Here is what a typical Mortgage will have included:
Occupancy. Borrower shall occupy, establish, and use the Property as Borrower's principal residence within 60 days after the execution of this Security Instrument and shall continue to occupy the Property as Borrower's principal residence for at least one year after the date of occupancy, unless Lender otherwise agrees in writing, which consent shall not be unreasonably withheld, or unless extenuating circumstances exist which are beyond Borrower's control.
If you breach your Mortgage, the lender can call the Note due.
Hope that helps!