For long term access I prefer to refi into fixed rate 30 year loans.  

For my C-Class rentals I do:-3.5X earnings-No prior evictions-625 credit score-1st month's rent and security deposit-No smoking or vaping on the property-Pets depends.

Plus it places us in our preferred investment area.

I prefer to go the HELOC route because you can use it like a checkbook and only use it when you need it. 

I prefer being 5-10% below market.

At least that's the setup I prefer, others may do something different.

@James Sebastian your response is pretty well thought out already, my only recommendation is to include a personal invitation for them to contact you directly by phone, email, U.S.mail, or thru your attorney if they prefer. 

What is preferred?

That is just our business preference.

Preferably one that actively purchases investments like you are purchasing.2) An investment specialized local realtorThese 2 specialists will give you a list of practical solutions, and then you can create a road map and the 3 of you can work in lockstep, with the same goals to get you there.