Those LOC's are more flexible than mortgages, but the terms are not usually as favorable (usually higher interest and lower LTV's.)

It seems that having savings in a brokerage accounts is the most flexible.

They have some more flexibility sometimes.

Rather than trying to fit Fannie's box, there's really something to be said about flexibility.  

(if they only require 15% down on a single family home that is usually a good sign that you are working with a flexible lender) Can I change title to my LLC?

If he buys it he now has more flexibility in what he does with his property, including any of the above options should they become relevant at some time in the future.

You have more flexibility this way vs a 15 year.. 

A 1031 requires a lot of things to line up just right, timing-wise, so if this is a deal you can make work, and you are able to offer timing flexibility, you may find you can negotiate a bit.

Ideally, you want one that is going to keep that loan on their books and will be more flexible.

I think a HELOC on your primary residence will give you flexibility to pounce when you find that right opportunity and you’ll not be making monthly payments in the interim, like you will with a conventional loan, while you wait to find the right investment.