I think part of the answer comes in the financing of the person buying your option at 90%. I dont think current guidelines will allow the financing of the option using a simultaneous close because you will have no title seasoning. It would not be an issue if you had a cash buyer, but there are few homeowners who are really cash buyers these days
However, it may work if you lease option the house and hold it for 90 days before re-selling it at the 90% level. Given todays market pace it is probably realistic to hold onto the option for 90 days total cycle anyways. You would need to verify that holding the lease option 90 days would suffice for title seasoning.
Just my .02 cents
Jim