Loan type question

[Melanie King]

Hello, I'm looking to buy a STR property with a loan and I'm wondering about advice for the type of loan. I've been given quotes for everything from 5 year ARMs, 5 year ARM IO, to 7 to 10 years of both of those on up to 30 year fixed. If rates really are going to come down it seems the 5 year ARM might be the smart play here but I'd love some experience to weigh in. I have one rental already that I paid cash for so this will be the first one I finance. I also have the option of a purchase mortgage with a pledge of the down payment from investments but don't have to actually put the money down, vs a conventional. They are higher payments but no $$ tied up. Or do I just go with the one that gives me the lowest mortgage payment of all of them which is a conventional 5 year ARM?

Thanks in advance! 
Melanie