In the current state there is no reason to get an ARM because the ARM rates are now higher then the 30 year fixed rates...
Interest rates are super low so the only way they can go is up.
Therefore ARMs would be a really REALLY stupid move right now.
PLUS over 18 months you will have no chance of recouping closing costs.
So you would save enough to cover the closing cost fees?
What is the point of even doing this? Just to lower payments?
Also although your escrow will be refunded you do not get to keep that money. That is for insurance and taxes and must go back in the new escrow. Otherwise you will come up short on escrow and they will adjust it UP big time.
Additionally you talk about renting it out. You cannot do that if you are FHA because mortgages are for primary residences only. Rental properties are for ballers than can afford to not go FHA...
It sounds like you have given this a lot of thought but at the end of the day my assessment is that it is a bad idea.
What about taking in a renting roommate to defray costs?
have you learned nothing from the last few months, ARM is one of the reasons so many got in such deep trouble...they gambled and lost big