Seeking advice on HELOC or cash out refinance

[Keith Foltz]

My wife and I are buy/hold and would like to add to our single family rentals. Here is our current situation:

Rental 1 has a loan balance of about $50k and would probably appraise around $120k

Rental 2 has close to the same numbers 

Rental 3 has a balance of $90k and about $150k value

Our primary has a balance of $180k and is being refinanced  this month and should appraise around $250k

We have never done a HELOC or cash out refinance, but we'd like to start being more aggressive and put some equity to work. We appreciate any input. Thank you.