Still confused regarding State Usury Laws

I’ve asked this question over the course of 2 years (not here, mind you) but I never seem to get a straight answer…Or, perhaps I never truly understood the answer I received.

I’m having trouble understanding whether or not MHP (& MH) loans must be at or under the state’s usury law.

For example: State of Illinois has usury of 9%, regardless if the current or future interest rate is higher or lower than 9%.

Say, I want to sell a mobile home or perhaps sell a MHP via seller financing. Whichever state it’s located. Do I must stay at or under that state’s maximum percentage? Or, does it not apply to Usury law?