Jace, what specific areas are you investing in?

I would probably go with a HELOC as you won't have to pay for what you're not using unless you've got a specific property you're going to be buying with that money so you know you won't just take out the loan and sit on it paying interest all the while. 

What was the outcome?

They might have insights on specific zip codes or pitfalls to avoid. https://www.biggerpockets.com/forums/521

This protects against potential claims and liabilities specific to the rental.For tax purposes, maintain clear records of rental-related income and expenses, allowing deductions for insurance, utilities, maintenance, and depreciation proportionate to the rental unit.

Quote from @Joshua Janus: Cleveland, Ohio is a great market to focus on for cash flow and specific pockets have gone up 2x and upwards of 4x in the last 5-10 years even!

Specifics on how to start are all appreciated!

Pre '2010', maybe just maybe it will lean heavier on the fundamental mechanics than specific processes. 

specifically AZ, NV TX, UT, WA and CA

Assuming it wasn't addressed in your PSA specifically then it likely should be them, but the reality is it is likely you.